Replace several uses of `console.warn` with `warnOnce`

The stub is re-initialized for every test, so there is no point in
checking at the start.

This reduces warning spam in the event where the code path that triggers
the warning is invoked repeatedly and there is no value to the developer
in telling them about the issue more than once.

To make `warnOnce` an easier drop-in replacement for `console.warn`, it
has been modified to accept multiple arguments, all of which get
forwarded to `console.warn`.

Upgrade Preact

Move firstKey function from sidebar-content to store

Add utility to re-render components when store changes

 - Simplify an example. `useCallback` is not required.
 - Add a comment regarding effect cleanup

This moves the firstKey function from the sidebar-content into
the selection store module.

Fix an issue where `GroupListItem` components did not re-render when the
focused group changed. This component is due to be replaced shortly, so
this is really just a test case to show that `useStore` works as
expected.

Add a hook that connects a store to a React/Preact component and ensures that
it re-renders when relevant store state changes.

Merge pull request #1141 from hypothesis/dependabot/npm_and_yarn/babel-plugin-transform-async-to-promises-0.8.11

Bump babel-plugin-transform-async-to-promises from 0.8.10 to 0.8.11

This fixes a code generation bug which broke the latest version of
babel-plugin-transform-async-to-promises.

Bump @octokit/rest from 16.26.0 to 16.27.0

Bump raven-js from 3.27.0 to 3.27.1

Bump express from 4.17.0 to 4.17.1

Bump @babel/core from 7.4.4 to 7.4.5

Bumps [babel-plugin-transform-async-to-promises](https://github.com/rpetrich/babel-plugin-transform-async-to-promises) from 0.8.10 to 0.8.11.
- [Release notes](https://github.com/rpetrich/babel-plugin-transform-async-to-promises/releases)
- [Commits](https://github.com/rpetrich/babel-plugin-transform-async-to-promises/compare/v0.8.10...v0.8.11)

Bump @babel/preset-env from 7.4.4 to 7.4.5

Bump core-js from 2.6.6 to 2.6.9

Bumps [express](https://github.com/expressjs/express) from 4.17.0 to 4.17.1.
- [Release notes](https://github.com/expressjs/express/releases)
- [Changelog](https://github.com/expressjs/express/blob/master/History.md)
- [Commits](https://github.com/expressjs/express/compare/4.17.0...4.17.1)

Bumps [raven-js](https://github.com/getsentry/raven-js) from 3.27.0 to 3.27.1.
- [Release notes](https://github.com/getsentry/raven-js/releases)
- [Changelog](https://github.com/getsentry/sentry-javascript/blob/master/CHANGELOG.md)
- [Commits](https://github.com/getsentry/raven-js/commits)

Bumps [@octokit/rest](https://github.com/octokit/rest.js) from 16.26.0 to 16.27.0.
- [Release notes](https://github.com/octokit/rest.js/releases)
- [Commits](https://github.com/octokit/rest.js/compare/v16.26.0...v16.27.0)

Bumps [@babel/core](https://github.com/babel/babel) from 7.4.4 to 7.4.5.
- [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/v7.4.4...v7.4.5)

Bumps [@babel/preset-env](https://github.com/babel/babel) from 7.4.4 to 7.4.5.
- [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/v7.4.4...v7.4.5)

Bumps [core-js](https://github.com/zloirock/core-js) from 2.6.6 to 2.6.9.
- [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/compare/v2.6.6...v2.6.9)

[Security] Bump tar from 2.2.1 to 2.2.2

Bumps [tar](https://github.com/npm/node-tar) from 2.2.1 to 2.2.2. **This update includes security fixes.**
- [Release notes](https://github.com/npm/node-tar/releases)
- [Commits](https://github.com/npm/node-tar/compare/v2.2.1...v2.2.2)

Format gulpfile.js and files in scripts/ using Prettier

Eliminate an inconsistency in the client codebase that most files are
formatted with Prettier but files in scripts/ and gulpfile.js were not.

Show focus indicator on various UI elements if they have keyboard focus

Bump express from 4.16.4 to 4.17.0

Bump prettier from 1.17.0 to 1.17.1

Bump @octokit/rest from 16.25.4 to 16.26.0

Bump codecov from 3.4.0 to 3.5.0

Bump core-js from 2.6.5 to 2.6.6

Bumps [prettier](https://github.com/prettier/prettier) from 1.17.0 to 1.17.1.
- [Release notes](https://github.com/prettier/prettier/releases)
- [Changelog](https://github.com/prettier/prettier/blob/master/CHANGELOG.md)
- [Commits](https://github.com/prettier/prettier/compare/1.17.0...1.17.1)
Signed-off-by: dependabot[bot] <support@dependabot.com>

Bumps [express](https://github.com/expressjs/express) from 4.16.4 to 4.17.0.
- [Release notes](https://github.com/expressjs/express/releases)
- [Changelog](https://github.com/expressjs/express/blob/master/History.md)
- [Commits](https://github.com/expressjs/express/compare/4.16.4...4.17.0)
Signed-off-by: dependabot[bot] <support@dependabot.com>