Because of the debouncing of mutation observer, sometimes 50ms was not
enough to trigger the callback function (`onFrameAdded`).

For the `FrameObserver` tests, I have disabled the debouncing. It has
the benefit that the test run faster now.

Remove a filter callback which always returned true. The first `!ann.id`
condition is already part of the `store.unsavedAnnotations` logic. The
second `isHighlight(...)` check did not work properly because the input
was an annotation stub object with only `id` and `$tag` fields instead
of the `Annotation` that `isHighlight` expects. For annotation stubs
with no id, it always returned false.

From a functional perspective the `isHighlight` check was also
unnecessary. `store.unsavedAnnotations()` only returns IDs of
annotations which have active drafts, but for highlights no draft is
created.

The newest version of the `createSelector` typings require the type of
the input argument to be determined in order for the whole call to
typecheck. This commit implements a pattern where:

- A `State` type is added in various store modules, typically defined as
  `typeof initialState`, that defines the state of that store module's
  type.
- The type of selector function params in `createSelector` calls is
  specified with `@param {State} state` and the return type is inferred

The upside of these changes is that types of selector functions are
determined much more robustly - previously it was possible to have
incorrect types specified via JSDoc.

In the process an existing minor bug was determined where an
`isHighlight` call in `ThreadList` was passed an unexpected type of
object (the `annotation` property of a `Draft`) for which `isHighlight`
did not crash but would always return false. I have simply suppressed
this existing issue for the moment, but it will need to be fixed
separately.

Bumps [reselect](https://github.com/reduxjs/reselect) from 4.0.0 to 4.1.1.
- [Release notes](https://github.com/reduxjs/reselect/releases)
- [Changelog](https://github.com/reduxjs/reselect/blob/master/CHANGELOG.md)
- [Commits](https://github.com/reduxjs/reselect/compare/v4.0.0...v4.1.1)

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This makes the structure consistent with LMS' styles

The boot script used to be generated in several stages:

 1. The files in `src/boot/` were bundled into `build/scripts/boot.bundle.js`
    with underscore-prefixed placeholders for certain data.

 2. A gulp task would generate `build/manifest.json` which included
    hashes of assets in the build dir

 3. Another gulp task would read `build/scripts/boot.bundle.js` and use
    string replacements to replace the placeholders with final values
    and write the result to `build/boot.js`

This commit simplifies the process by combining stage (1) and (3). Add a
separate Rollup config, rollup-boot.config.mjs, which builds
`build/boot.js` directly from the `src/boot/index.js` entry point, using
@rollup/plugin-replace to replace placeholders with data during the
build.

The code to generate the manifest in step (2) has been replaced with the
manifest-generation code from the @hypothesis/frontend-build package,
which is also shared with other projects.

This change allows removal of several dependencies from the project, and
means that we only have one way to replace `__PLACEHOLDER__`
placeholders in JS files during the build, rather than two different
ones.

One minor change here is that only JS, CSS and sourcemap files are
referenced in the manifest. Font files are not mentioned since the code
that loads them (KaTeX) doesn't make use of the manifest.

* Use `LabeledButton` instead of custom `<button>`
* Use `Icon`, `Frame` components where useful
* Reduce local/custom CSS
* Modernize tests
* Add title to `Icon` for a11y

Fixes https://github.com/hypothesis/support/issues/241

Part of https://github.com/hypothesis/client/issues/3876

Part of https://github.com/hypothesis/frontend-shared/issues/232

These rules were added 10 years ago. We don't have any `sup` or `sub`
elements in our source, and they could have possibly deleterious effects
when user content is styled.

Part of https://github.com/hypothesis/frontend-shared/issues/208

Part of https://github.com/hypothesis/frontend-shared/issues/232

These are interim until we establish a typography pattern layer, and
are intended to keep individual font rules from littering component styles.

Add a local patterns SASS module as a place to isolate and stage local
app patterns for potential extraction to shared package.

Bumps [karma](https://github.com/karma-runner/karma) from 6.3.5 to 6.3.6.
- [Release notes](https://github.com/karma-runner/karma/releases)
- [Changelog](https://github.com/karma-runner/karma/blob/master/CHANGELOG.md)
- [Commits](https://github.com/karma-runner/karma/compare/v6.3.5...v6.3.6)

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Bumps [aws-sdk](https://github.com/aws/aws-sdk-js) from 2.1013.0 to 2.1018.0.
- [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/v2.1013.0...v2.1018.0)

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Bumps [rollup](https://github.com/rollup/rollup) from 2.58.3 to 2.59.0.
- [Release notes](https://github.com/rollup/rollup/releases)
- [Changelog](https://github.com/rollup/rollup/blob/master/CHANGELOG.md)
- [Commits](https://github.com/rollup/rollup/compare/v2.58.3...v2.59.0)

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Bumps [@babel/preset-react](https://github.com/babel/babel/tree/HEAD/packages/babel-preset-react) from 7.14.5 to 7.16.0.
- [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/v7.16.0/packages/babel-preset-react)

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Bumps [@babel/core](https://github.com/babel/babel/tree/HEAD/packages/babel-core) from 7.15.8 to 7.16.0.
- [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/v7.16.0/packages/babel-core)

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Per the release notes in https://github.com/hypothesis/client/pull/3887,
KaTeX should be imported using a default import rather than namespace
import.

Bumps [redux-thunk](https://github.com/reduxjs/redux-thunk) from 2.3.0 to 2.4.0.
- [Release notes](https://github.com/reduxjs/redux-thunk/releases)
- [Commits](https://github.com/reduxjs/redux-thunk/compare/v2.3.0...v2.4.0)

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Bumps [axe-core](https://github.com/dequelabs/axe-core) from 4.3.3 to 4.3.5.
- [Release notes](https://github.com/dequelabs/axe-core/releases)
- [Changelog](https://github.com/dequelabs/axe-core/blob/v4.3.5/CHANGELOG.md)
- [Commits](https://github.com/dequelabs/axe-core/compare/v4.3.3...v4.3.5)

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Bumps [katex](https://github.com/KaTeX/KaTeX) from 0.13.18 to 0.15.1.
- [Release notes](https://github.com/KaTeX/KaTeX/releases)
- [Changelog](https://github.com/KaTeX/KaTeX/blob/main/CHANGELOG.md)
- [Commits](https://github.com/KaTeX/KaTeX/compare/v0.13.18...v0.15.1)

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Bumps [redux](https://github.com/reduxjs/redux) from 4.1.1 to 4.1.2.
- [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/v4.1.1...v4.1.2)

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Bumps [@babel/preset-env](https://github.com/babel/babel/tree/HEAD/packages/babel-preset-env) from 7.15.8 to 7.16.0.
- [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/v7.16.0/packages/babel-preset-env)

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  dependency-type: direct:development
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Bumps [autoprefixer](https://github.com/postcss/autoprefixer) from 10.3.7 to 10.4.0.
- [Release notes](https://github.com/postcss/autoprefixer/releases)
- [Changelog](https://github.com/postcss/autoprefixer/blob/main/CHANGELOG.md)
- [Commits](https://github.com/postcss/autoprefixer/compare/10.3.7...10.4.0)

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  dependency-type: direct:development
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