- Use the string "blank" instead of `null` as a more explicit indicator
   that a menu item should show a blank space for an icon
 - Rename two variables to indicate their boolean-ness

The icon is from the Hypothicons set at https://hypothicons.netlify.com

Following a design review, adjust the styling of menus and in particular the
groups menu to better match the mocks [1] and create better separation between
different elements.

- Add a 10px margin below section headers
- Add a subtle border at bottom of expanded submenus
- Remove red hover color for menu items
- Make submenu items slightly lighter and darken them on hover
- Reduce font size to match top bar and reduce font weight for submenu items
- Increase submenu toggle caret size slightly (10 => 12px) and darken
  the caret on hover, consistent with the effect when submenu items are
  hovered.
- Avoid hyphenating messages in the footer of group list submenus

[1] https://sketch.cloud/s/D0OMk/a/EbnxQA/play

Bump focus-visible from 4.1.5 to 5.0.0

Bump @octokit/rest from 16.28.0 to 16.28.2

Merge pull request #1176 from hypothesis/dependabot/npm_and_yarn/babel-plugin-transform-async-to-promises-0.8.12

Bump babel-plugin-transform-async-to-promises from 0.8.11 to 0.8.12

Bump enzyme-adapter-preact-pure from 1.13.4 to 2.0.0

This test happened to pass before, but failed after an adapter upgrade.
All external state changes should be wrapped in `act` to flush state
updates and effects and followed by `wrapper.update` to update the
Enzyme adapter.

Bumps [@octokit/rest](https://github.com/octokit/rest.js) from 16.28.0 to 16.28.2.
- [Release notes](https://github.com/octokit/rest.js/releases)
- [Commits](https://github.com/octokit/rest.js/compare/v16.28.0...v16.28.2)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Bumps [enzyme-adapter-preact-pure](https://github.com/preactjs/enzyme-adapter-preact-pure) from 1.13.4 to 2.0.0.
- [Release notes](https://github.com/preactjs/enzyme-adapter-preact-pure/releases)
- [Changelog](https://github.com/preactjs/enzyme-adapter-preact-pure/blob/master/CHANGELOG.md)
- [Commits](https://github.com/preactjs/enzyme-adapter-preact-pure/compare/v1.13.4...v2.0.0)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Bumps [babel-plugin-transform-async-to-promises](https://github.com/rpetrich/babel-plugin-transform-async-to-promises) from 0.8.11 to 0.8.12.
- [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/v0.8.11...v0.8.12)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Bumps [focus-visible](https://github.com/WICG/focus-visible) from 4.1.5 to 5.0.0.
- [Release notes](https://github.com/WICG/focus-visible/releases)
- [Commits](https://github.com/WICG/focus-visible/compare/v4.1.5...v5.0.0)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Convert loading spinner to Preact

Remove passing of search

Previously a search object was built inside the hypothesis-app
component and passed down to its child components. Now, just use
the store.getState().filterQuery directly. This avoids unnecessarily
passing things between components and a layer of indirection between
the search object and the value in the store. Rename searchQuery to
filterQuery.

Simplify groups service `load` method using async/await

As per previous commit, it is currently possible for client
configuration to specify both an annotation to focus and an additional
group to include.

Move sidebar-content funcs to search-status-bar

Convert `help-link` component to preact

- filterMatchCount
- areAllAnnotationsVisible
- Remove passing of total-count as it's not used.

- Add tests

Replace help icon with lighter variant

- Add `height` rule to `top-bar__btn` to help with alignment

Implement new groups menu design built on groups menu

Also mock the `MenuItem` component manually so that any problems with
that component won't cause a cascade of failures in `GroupListItem`.

This covers the functionality related to the submenu for group list items.

Conditionally rendered items create boolean `false` entries in the
`children` prop when the condition is false.

To indicate that there are no special restrictions on the `children`
prop here beyond them being some kind of renderable content, I've opted
for the `any` prop type.

Avoid showing a focus ring on the item when activating it via
touch/mouse for consistency with how other tab-reachable parts of the
menu and top bar work.

Group names are user supplied and can be up to 25 chars, so allow more
space for this.

This can be used to set a custom minimum width for a particular menu for
example.

The name of the "groups" service is slightly ambiguous in this context.
We can't rename the prop because service dependencies are resolved by
name and the service is called "groups" when registered with Angular.

Convert portions of login-control component to (preact) UserMenu component