Bump mocha from 7.0.1 to 7.1.2

Bump terser from 4.6.11 to 4.6.12

Work around issue with Node v14 and Puppeteer

Bumps [aws-sdk](https://github.com/aws/aws-sdk-js) from 2.660.0 to 2.663.0.
- [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/v2.660.0...v2.663.0)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Use the system version of Chrome if the developer has Node v14
installed, to work around an upstream issue with Puppeteer (see code
comment).

Bumps [terser](https://github.com/terser/terser) from 4.6.11 to 4.6.12.
- [Release notes](https://github.com/terser/terser/releases)
- [Changelog](https://github.com/terser/terser/blob/master/CHANGELOG.md)
- [Commits](https://github.com/terser/terser/compare/v4.6.11...v4.6.12)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Bumps [@octokit/rest](https://github.com/octokit/rest.js) from 17.5.1 to 17.6.0.
- [Release notes](https://github.com/octokit/rest.js/releases)
- [Commits](https://github.com/octokit/rest.js/compare/v17.5.1...v17.6.0)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Bumps [mocha](https://github.com/mochajs/mocha) from 7.0.1 to 7.1.2.
- [Release notes](https://github.com/mochajs/mocha/releases)
- [Changelog](https://github.com/mochajs/mocha/blob/master/CHANGELOG.md)
- [Commits](https://github.com/mochajs/mocha/compare/v7.0.1...v7.1.2)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Bump karma-mocha from 1.3.0 to 2.0.0

Convert stream content to Preact

This is a fairly direct conversion of the `<stream-content>` component
from AngularJS to Preact.

There is one minor improvement which is to display an error notification
if fetching annotations from the API fails.

Convert single annotation page content to Preact

- Allow keyboard navigation of menus
- Fix various menu a11y issues
- Fix one underlying issue where executing a link in the menu with keyboard (Enter or Space) never worked
- Add MenuKeyboardNavigation helper component

Bump aws-sdk from 2.658.0 to 2.660.0

Move margin between `ThreadCard`s to `ThreadList`

Fix overflow on Thread contents

Add `overflow:hidden` to `.thread__content` containers such that long
un-breaking words (e.g. URLs) don’t break the sidebar width on nested
replies.

Fixes https://github.com/hypothesis/support/issues/101

Add differentiating link styling to tutorial

Several new developers have in the past asked why we use virtualization
since it adds complexity to the thread list implementation. Add a note
to the `ThreadList` docs explaining why it is needed.

Move the bottom margin on thread cards from the root `<div>` rendered by
`ThreadCard` to the wrapper div that contains it rendered by
`ThreadList`.

Aside from making conceptual sense that the list component controls the
spacing of list items, this also fixes an issue where the thread list
would sometimes jump when scrolling. This happened because the height of
individual threads was computed by calling `getElementHeightWithMargins`
on the wrapper div, which only accounted for margins on the wrapper div,
not margins on descendants. Note that due to margin collapsing, the descendant
margins did not contribute to the `getBoundingClientRect()` of the
wrapper div.

This normalizes the key names for events from non-standard browsers like IE11

Bumps [dompurify](https://github.com/cure53/DOMPurify) from 2.0.8 to 2.0.9.
- [Release notes](https://github.com/cure53/DOMPurify/releases)
- [Commits](https://github.com/cure53/DOMPurify/compare/2.0.8...2.0.9)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Fixes #2054

Remove `FRAME_CONNECTED` event

Bump preact from 10.4.0 to 10.4.1

Bump @sentry/browser from 5.15.4 to 5.15.5

Bumps [preact](https://github.com/preactjs/preact) from 10.4.0 to 10.4.1.
- [Release notes](https://github.com/preactjs/preact/releases)
- [Commits](https://github.com/preactjs/preact/compare/10.4.0...10.4.1)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Bump puppeteer from 3.0.0 to 3.0.1

Bump prettier from 2.0.4 to 2.0.5

Do not use `button` element in `Menu` label

There is not a lot of point in testing this at the moment because the
expected behavior in this case isn't really defined, other than "doesn't
generate an error", and since we have no means of displaying that error,
there is nothing a test can readily check for.

This is a pretty direct conversion of the `<annotation-viewer-content>`
component from AngularJS to Preact.

Much of the logic and tests are for non-UI logic, so could potentially
be moved to a service in future.

I encountered an odd issue with the `fetchThread` helper that required
it to be put at the bottom of the file. Putting it at the top resulted
in an error related to the `createElement` import at runtime.

An issue relating to the highlighting of which reply the ID in the URL
refers to is noted in the code. What should happen is that the reply
that the ID in the URL refers to is visually highlighted. This is an
existing regression from before this commit.

Menu labels are already rendered within a `button` element, so they
may not contain a `button` themselves, or else invalid HTML structure

Migrate `ThreadList` to preact

- Disable scroll anchoring, as it interferes with `ThreadList` and the
  calculation of visual threads and can cause infinite render loops
- Make scroll position in `ThreadList` fuzzier (50 px precision) to
  reduce scroll-event-related re-renders
- Improve test structure in `ThreadList` for these changes and better
  coverage

- Replace ng-1 `thread-list` with preact `ThreadList`
  (renamed from `ThreadListOmega`)
- Remove SCSS (new `ThreadList` has no CSS)
- Remove `virtual-thread-list`