Because of recent changes in the sidebar (#2904), the BucketBar
component is no longer used as a plugin. @robertknight suggested to
remove all unneeded functionality.

Closes #2907

On PR #2904, it was forgotten to pass the bucket bar options to the
constructor.

Closes #3047

Remove entries that refer to dependencies that are no longer used by the
client or update restrictions that no longer apply. These were
automatically imported from Dependabot's config and never got pruned
when they became obsolete.

Bumps [typescript](https://github.com/Microsoft/TypeScript) from 4.1.3 to 4.1.5.
- [Release notes](https://github.com/Microsoft/TypeScript/releases)
- [Commits](https://github.com/Microsoft/TypeScript/compare/v4.1.3...v4.1.5)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Bumps [mocha](https://github.com/mochajs/mocha) from 8.2.1 to 8.3.0.
- [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/v8.2.1...v8.3.0)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Bumps [@sentry/browser](https://github.com/getsentry/sentry-javascript) from 6.1.0 to 6.2.0.
- [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/6.1.0...6.2.0)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Bumps [sass](https://github.com/sass/dart-sass) from 1.32.7 to 1.32.8.
- [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/1.32.7...1.32.8)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Bumps [@babel/preset-env](https://github.com/babel/babel/tree/HEAD/packages/babel-preset-env) from 7.12.13 to 7.12.17.
- [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/v7.12.17/packages/babel-preset-env)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Bumps [aws-sdk](https://github.com/aws/aws-sdk-js) from 2.839.0 to 2.848.0.
- [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/v2.839.0...v2.848.0)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Bumps [@octokit/rest](https://github.com/octokit/rest.js) from 18.1.0 to 18.2.0.
- [Release notes](https://github.com/octokit/rest.js/releases)
- [Commits](https://github.com/octokit/rest.js/compare/v18.1.0...v18.2.0)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Bumps [@babel/core](https://github.com/babel/babel/tree/HEAD/packages/babel-core) from 7.12.16 to 7.12.17.
- [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/v7.12.17/packages/babel-core)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

These custom names were a method of reducing the likelihood of these
elements being affected by the page's CSS. Since Shadow DOM support is
now much more ubiquitous this is not an issue, so switch back to
ordinary `<div>`s.

Note that the shadow hosts still use custom element names to prevent
them being impacted by page styles.  The elements being changed here are
inside the shadow DOM.

Add a new `/ui-playground` route to the client's dev server which hosts
a UI component playground/demo app, plus a link to this route on the dev
server homepage. The demo app provides a place to see and experiment with
UI components outside the context of the sidebar/notebook apps.

 - Add new `/ui-playground` route to dev server which serves a small
   Preact SPA

 - Add Preact SPA in `dev-server/ui-playground/` with a couple of
   placeholder "demos" for the `Button` and `Menu` components

 - Add configuration to gulpfile.js to build ui-playground JS and CSS
   bundles for Preact SPA

- Update NotebookView to corral pagination, Notebook-y state
- Update NotebookResultCount to be dumber
  (to balance with PaginatedThreadList)
- Integrate PaginatedThreadList into NotebookView

Add a PaginatedThreadList component, which renders pagination controls.
This component is not yet hooked up to anything.

- Add a component to render pagination controls
- Component is unused

- Add a utility function for generating the right set of available
  pagination page numbers, given `currentPage`, `totalPages` and
  the maximum number of page options desired

- Make `Button` take `iconPosition` prop {`left|right`} to allow for
  right-aligned icons on buttons
- Add parameters to `button--labeled` mixin to allow for background
  color overrides

This test isn't meaningful as a number of other tests would fail if
sub-components were rendered without the presence of an `annotation`

Leave class naming alone for now, as these modules haven't been fully
normalized/component-ized yet.

Bumps [puppeteer](https://github.com/puppeteer/puppeteer) from 5.5.0 to 7.1.0.
- [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/v5.5.0...v7.1.0)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

The feature test for the `CSS.supports` API did not work in the most
recent versions of Chrome or in Firefox because `typeof CSS` returns
`object` in those browsers. In Safari and older versions of Chrome it
returns `function`. This change most likely occurred due to
https://chromium-review.googlesource.com/c/chromium/src/+/2434404.

All of the browsers we currently support implement the two-argument
version of `CSS.supports` (see [1]) and so we can fix the issue by removing the feature test.

Note that the single-argument version of `CSS.supports` is not supported
by some of the oldest browsers that we support.

[1] https://developer.mozilla.org/en-US/docs/Web/API/CSS/supports#browser_compatibility

Bumps [postcss](https://github.com/postcss/postcss) from 8.2.5 to 8.2.6.
- [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/8.2.5...8.2.6)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Bumps [axe-core](https://github.com/dequelabs/axe-core) from 4.1.1 to 4.1.2.
- [Release notes](https://github.com/dequelabs/axe-core/releases)
- [Changelog](https://github.com/dequelabs/axe-core/blob/develop/CHANGELOG.md)
- [Commits](https://github.com/dequelabs/axe-core/compare/v4.1.1...v4.1.2)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Bumps [karma](https://github.com/karma-runner/karma) from 6.1.0 to 6.1.1.
- [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/v6.1.0...v6.1.1)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Bumps [sass](https://github.com/sass/dart-sass) from 1.32.6 to 1.32.7.
- [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/1.32.6...1.32.7)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Bumps [commander](https://github.com/tj/commander.js) from 7.0.0 to 7.1.0.
- [Release notes](https://github.com/tj/commander.js/releases)
- [Changelog](https://github.com/tj/commander.js/blob/master/CHANGELOG.md)
- [Commits](https://github.com/tj/commander.js/compare/v7.0.0...v7.1.0)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Bumps [@babel/core](https://github.com/babel/babel/tree/HEAD/packages/babel-core) from 7.12.10 to 7.12.16.
- [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/v7.12.16/packages/babel-core)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Bumps [eslint](https://github.com/eslint/eslint) from 7.19.0 to 7.20.0.
- [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/v7.19.0...v7.20.0)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

When Shadow DOM was first considered for use in the client `<link
rel="stylesheet">` was not widely supported as a way to load external styles into
shadow roots. This was resolved in the spec in https://github.com/whatwg/html/pull/1572
and has now long been supported by all browsers.

Using `<link>` simplifies the code and also avoids a possible problem with sites
that have a strict CSP policy that disallows inline styles. In the
browser extension context a `<link>` can still work in that scenario as long as the
stylesheet is loaded from a `chrome-extension://` URL.