Bump @sentry/browser from 5.11.1 to 5.11.2

Improve a11y testing for AutocompleteList and TagEditor

- TagEditor test renders full AutocompleteList for end to end a11y test
- AutocompleteList now uses a `is-hidden` class rather than preact to hide itself. This was necessary to pass a11y lint.
- Change TagEditor to unset the activeIndex when adding tag
- Add `aria-label` to TagEditor <input> filed, `placeholder` attr not sufficient for lint
- Very slight color adjust on $grey-5 to keep 4.5:1 contrast spec

Move component test utilities to src/test-util/

Bump commander from 4.1.0 to 4.1.1

Bump puppeteer from 2.0.0 to 2.1.0

Merge pull request #1744 from hypothesis/dependabot/npm_and_yarn/babel-plugin-mockable-imports-1.7.0

Bumps [@babel/core](https://github.com/babel/babel) from 7.8.3 to 7.8.4.
- [Release notes](https://github.com/babel/babel/releases)
- [Changelog](https://github.com/babel/babel/blob/master/CHANGELOG.md)
- [Commits](https://github.com/babel/babel/compare/v7.8.3...v7.8.4)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Bumps [@babel/preset-env](https://github.com/babel/babel) from 7.8.3 to 7.8.4.
- [Release notes](https://github.com/babel/babel/releases)
- [Changelog](https://github.com/babel/babel/blob/master/CHANGELOG.md)
- [Commits](https://github.com/babel/babel/compare/v7.8.3...v7.8.4)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Bumps [@sentry/browser](https://github.com/getsentry/sentry-javascript) from 5.11.1 to 5.11.2.
- [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/5.11.1...5.11.2)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Bumps [@octokit/rest](https://github.com/octokit/rest.js) from 16.38.3 to 16.43.0.
- [Release notes](https://github.com/octokit/rest.js/releases)
- [Commits](https://github.com/octokit/rest.js/compare/v16.38.3...v16.43.0)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Bumps [babel-plugin-mockable-imports](https://github.com/robertknight/babel-plugin-mockable-imports) from 1.6.0 to 1.7.0.
- [Release notes](https://github.com/robertknight/babel-plugin-mockable-imports/releases)
- [Changelog](https://github.com/robertknight/babel-plugin-mockable-imports/blob/master/CHANGELOG.md)
- [Commits](https://github.com/robertknight/babel-plugin-mockable-imports/compare/v1.6.0...v1.7.0)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Bumps [dompurify](https://github.com/cure53/DOMPurify) from 2.0.7 to 2.0.8.
- [Release notes](https://github.com/cure53/DOMPurify/releases)
- [Commits](https://github.com/cure53/DOMPurify/compare/2.0.7...2.0.8)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Bumps [puppeteer](https://github.com/puppeteer/puppeteer) from 2.0.0 to 2.1.0.
- [Release notes](https://github.com/puppeteer/puppeteer/releases)
- [Commits](https://github.com/puppeteer/puppeteer/compare/v2.0.0...v2.1.0)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Bumps [commander](https://github.com/tj/commander.js) from 4.1.0 to 4.1.1.
- [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/v4.1.0...v4.1.1)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Chrome extension did not upload correctly, bumping version to repeat the travis build

Improve organizational clarity by separating tests from utility modules
used in tests, and also pave the way for re-using these utilities for UI
outside the sidebar app in future (eg. src/annotator/).

Improved tag editor (Part 2/2)

- Fix add new tag bug in Edge
- Remove tag-editor’s Chrome hack fix to limit suggestions to 20
- Add ARIA 1.1 Combobox  a11y model to TagEditor

Add accessibility unit test using axe-core

"default" is the default name for an a11y scenario unless one is
specified.

Remove the global react/display-name lint suppression for the
src/sidebar/components/test directory with individual line-level
suppressions.

The reason for having a global rule wasn't obvious when looking at
.eslintrc and there aren't that many occurrences.

Improve handling of text in RTL languages

This enables axe-core tests which depend on CSS rules being available to
work, such as checking that elements have sufficient color contrast.

Remove obsolete references to shallow rendering

`checkAccessibility` calls often violate this rule because the `content`
key is assigned a function which returns an element, but is not actually
a component.

Add Datalist component (Part 1/2)

- Use as a replacement for the native <datalist> tag
- Fix UI differences between Chrome, FF, Safari and Edge with respect to the <datalist>
- Fix performance issues experienced in Chrome when used with <datalist>
- Allow for future enhanced customization of list including substring highlighting that <datalist> could not do

Add infrastructure for running a11y tests using axe-core and add an
initial set of tests for existing components. A small number of
components (3) fail these checks. These tests have been temporarily
skipped so that we can incrementally fix them later.

One trivial issue with an un-labeled link in `LoggedOutMessage` was fixed by
adding a `title` attribute.

We replaced use of Enzyme's shallow rendering for component unit tests
some time ago in https://github.com/hypothesis/client/pull/1470.

Add eslint-plugin-jsx-a11y to the lint configuration

Bump cross-env from 6.0.3 to 7.0.0

Bump fetch-mock from 8.3.1 to 8.3.2

Bump sinon from 8.1.0 to 8.1.1