Move the logic for scrolling the content to the highlights associated
with an anchor from `Guest` to the content-type specific integration
(`HTMLIntegration`, `PDFIntegration`). The implementations of this logic
in `HTMLIntegration` and `PDFIntegration` are currently the same as
before, but in future this will allow adapting the scrolling logic to
the content type.

In the case of PDFs the logic will need to allow for the fact that an
annotation may be re-anchored to a different element as the document is
scrolled due to the page containing the annotation changing between an
un-rendered and rendered state.

 - Add `scrollToAnchor` method to `Integration` interface and implement
   it for `HTMLIntegration`, `PDFIntegration`
 - Replace `scrollIntoView` call in guest with a call to the active
   integration's `scrollToAnchor` method

Bumps [katex](https://github.com/KaTeX/KaTeX) from 0.13.2 to 0.13.3.
- [Release notes](https://github.com/KaTeX/KaTeX/releases)
- [Changelog](https://github.com/KaTeX/KaTeX/blob/master/CHANGELOG.md)
- [Commits](https://github.com/KaTeX/KaTeX/compare/v0.13.2...v0.13.3)
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Bumps [gulp-replace](https://github.com/lazd/gulp-replace) from 1.0.0 to 1.1.1.
- [Release notes](https://github.com/lazd/gulp-replace/releases)
- [Commits](https://github.com/lazd/gulp-replace/commits)
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Bumps [@babel/core](https://github.com/babel/babel/tree/HEAD/packages/babel-core) from 7.13.15 to 7.13.16.
- [Release notes](https://github.com/babel/babel/releases)
- [Changelog](https://github.com/babel/babel/blob/main/CHANGELOG.md)
- [Commits](https://github.com/babel/babel/commits/v7.13.16/packages/babel-core)
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Bumps [postcss](https://github.com/postcss/postcss) from 8.2.10 to 8.2.12.
- [Release notes](https://github.com/postcss/postcss/releases)
- [Changelog](https://github.com/postcss/postcss/blob/main/CHANGELOG.md)
- [Commits](https://github.com/postcss/postcss/compare/8.2.10...8.2.12)
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Bumps [aws-sdk](https://github.com/aws/aws-sdk-js) from 2.888.0 to 2.892.0.
- [Release notes](https://github.com/aws/aws-sdk-js/releases)
- [Changelog](https://github.com/aws/aws-sdk-js/blob/master/CHANGELOG.md)
- [Commits](https://github.com/aws/aws-sdk-js/compare/v2.888.0...v2.892.0)
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Bumps [@octokit/rest](https://github.com/octokit/rest.js) from 18.5.2 to 18.5.3.
- [Release notes](https://github.com/octokit/rest.js/releases)
- [Commits](https://github.com/octokit/rest.js/compare/v18.5.2...v18.5.3)
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Bumps [core-js](https://github.com/zloirock/core-js/tree/HEAD/packages/core-js) from 3.10.1 to 3.11.0.
- [Release notes](https://github.com/zloirock/core-js/releases)
- [Changelog](https://github.com/zloirock/core-js/blob/master/CHANGELOG.md)
- [Commits](https://github.com/zloirock/core-js/commits/v3.11.0/packages/core-js)
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Bumps [eslint](https://github.com/eslint/eslint) from 7.24.0 to 7.25.0.
- [Release notes](https://github.com/eslint/eslint/releases)
- [Changelog](https://github.com/eslint/eslint/blob/master/CHANGELOG.md)
- [Commits](https://github.com/eslint/eslint/compare/v7.24.0...v7.25.0)
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Bumps [terser](https://github.com/terser/terser) from 5.6.1 to 5.7.0.
- [Release notes](https://github.com/terser/terser/releases)
- [Changelog](https://github.com/terser/terser/blob/master/CHANGELOG.md)
- [Commits](https://github.com/terser/terser/commits)
Signed-off-by: dependabot[bot] <support@github.com>

Bumps [sass](https://github.com/sass/dart-sass) from 1.32.10 to 1.32.11.
- [Release notes](https://github.com/sass/dart-sass/releases)
- [Changelog](https://github.com/sass/dart-sass/blob/master/CHANGELOG.md)
- [Commits](https://github.com/sass/dart-sass/compare/1.32.10...1.32.11)
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Bumps [puppeteer](https://github.com/puppeteer/puppeteer) from 8.0.0 to 9.0.0.
- [Release notes](https://github.com/puppeteer/puppeteer/releases)
- [Changelog](https://github.com/puppeteer/puppeteer/blob/main/CHANGELOG.md)
- [Commits](https://github.com/puppeteer/puppeteer/compare/v8.0.0...v9.0.0)
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Bumps [@sentry/browser](https://github.com/getsentry/sentry-javascript) from 6.2.5 to 6.3.1.
- [Release notes](https://github.com/getsentry/sentry-javascript/releases)
- [Changelog](https://github.com/getsentry/sentry-javascript/blob/master/CHANGELOG.md)
- [Commits](https://github.com/getsentry/sentry-javascript/compare/6.2.5...6.3.1)
Signed-off-by: dependabot[bot] <support@github.com>

Bumps [redux](https://github.com/reduxjs/redux) from 4.0.5 to 4.1.0.
- [Release notes](https://github.com/reduxjs/redux/releases)
- [Changelog](https://github.com/reduxjs/redux/blob/master/CHANGELOG.md)
- [Commits](https://github.com/reduxjs/redux/compare/v4.0.5...v4.1.0)
Signed-off-by: dependabot[bot] <support@github.com>

Part of https://github.com/hypothesis/client/issues/3298

Checking `typeof <var>` is only needed when the variable may not exist
(eg. some browser global).

Put the logic for getting the grant token in one place so it can be
better documented.

Also remove or simplify some other code slightly upon a second reading.

A call to `refreshAccessToken` is not the only way that the token can
change while waiting for a response to the `POST /api/token` endpoint.

The previous name was a vestige from the days of Angular 1.x in the
client. Use a clearer name instead.

Refactor and better document the `tokenGetter` method to make it easier
to follow:

 - Split some sub-steps out into helper methods
 - Add comments to call out the high-levels steps in the flow

Extract a helper from a long async method to shorten it.

Make several functions/methods in the service easier to follow by
refactoring promise chains to async/await.

 - Add tests for `scrollToAnnotation`

 - Add test for failed `getDocumentInfo` request to host page

Convert the `frameSync` service to an ES class and rewrite the
documentation that explains what the service does.

Some internal `frameSync` methods are still set up in the constructor
with closures. These can be converted to ES class methods in later
refactoring.

Part of https://github.com/hypothesis/client/issues/3298.

Chrome 89 printed the following warnings on the console:

```
shadow-root.js:67 [Violation] Added non-passive event listener to a scroll-blocking 'touchstart' event. Consider marking event handler as 'passive' to make the page more responsive
```

See also: https://www.chromestatus.com/feature/5745543795965952

I have removed a listener that it isn't no longer needed, because it is wrapped in
a shadow DOM that already stop the bubbling up of the event.

Another 'touchstart' listener had the potential to slow down scrolling
on the host page on mobile devices. To avoid that we have made listener
passive.

These changes remove the warnings without affecting the current
behaviour of the application.

Move the logic for retrying API metadata fetching into the `getJSON`
helper function so that it is used both when fetching the API index
(`/api`) and the service links (`/api/links`).

Rename property from `params` to `unusedParams` for clarity.

Change the way that links pointing into the Hypothesis service (eg. for
tags, users, account settings etc.) are fetched and generated. The new
implementation better matches patterns used elsewhere in the application
and ensures that UI components displaying these links re-render if the
`/api/links` response is received after the component is initially
rendered.

 - Move the logic for rendering the URL templates from the `serviceUrl`
   service into a selector in the `links` store module. Components then
   render links using `store.getLink(...)`. This ensures use of the existing
   mechanism that re-renders components when relevant store data changes.

 - Convert the `serviceUrl` service to an ES class

 - Move the logic for fetching URL templates from the `/api/links`
   endpoint into an `init` method of the `ServiceURLService` service.
   This matches the convention used by several other services.

 - Remove unused `serviceUrl` dependency from `groups` service

As noted in a comment, the check is mainly intended to prevent infinite
loops in tests.

The name options implies a misc bag of optional properties, whereas this
is a mandatory set of callbacks.

This found a mistake in the types of several references to the document
URI, which is not always present.

This found an error in some of the existing types in the `api` service.

Refactor this class to new conventions as part of
https://github.com/hypothesis/client/issues/3298.

 - Convert the `auth` service to an ES class
 - Replace the internal `emitter` variable with inheritance
 - Rename the module from `oauth-auth.js` to just `auth.js`. The
   previous name is a vestige from when authorization was migrated from
   cookie-based to OAuth-based

 - Convert `features` service to a class

 - Remove the unused `flagEnabled` method. Calls to this method have
   gradually been replaced by `store.isFeatureEnabled`.

 - Move the initialization of the background sidebar => annotator
   synchronization of feature flag information into an `init` method
   which is then called from the sidebar's entry point. This pattern is
   consistent with several other services. It is also necessary for services
   that are not depended upon by anything else because services are
   lazily instantiated.

Put all the initialization logic in one place instead of spreading it
between the constructor and `init` method.

Part of https://github.com/hypothesis/client/issues/3298