Add a `lang=""` attribute to the annotation quote, body and tag list in
the UI which display content chosen or generated by the user, to
indicate to the user agent that the language is unknown and may be
different than the client UI, which is currently always English.

Part of https://github.com/hypothesis/client/issues/1794.

Refactor `SidebarContentError` for a11y, usability

Add `flex-shrink` rule to login links

Refactor `SidebarContentError` to be simpler and provide a clearer
UX for the four possible states of direct-linked errors (states are based
on error type—annotation or group—and whether the user is logged in or
not).

Reuse sidebar-panel design pattern overall.

Provide an option for the user to “clear the error”, i.e., show all
annotations instead of “filtering” by the direct-linked annotation or
group. Provide a button for the user to log in if they are not currently
logged in.

Update `SearchStatusBar` to remove unneeded references to direct-linked
store information, as it will now not render if there is a direct-linked
error.

Add a `flex-shrink` rule to the login links in the `TopBar` component
to assure that they don’t get all squished up when a search is active.

Replace link with `Button` in `AnnotationHeader` (A11y)

Fixes a11y-linting issue.

Part of https://github.com/hypothesis/client/issues/1727

Fix AutocompleteList aria-selecterd prop

Fix a11y lint on SelectionTabs component

Fix a11y for Excerpt

Remove jQuery dependency from highlighter and add test for multiple text nodes

AnnotationOmega: Add very basic expand/collapse for reply threads

As part of an ongoing project to remove the annotator's jQuery
dependency, rewrite the highlighter to avoid it.

This change is also preparation for some upcoming changes to make
highlights more friendly for screen reader users by reducing the
number of `<hypothesis-highlight>` elements created for a run of text in
various situations. Since each `<hypothesis-highlight>` announces its
presence to the screen reader, this gets "noisy" if there are many such
elements.

Convert ‘Log in’ and ‘Sign up’ links to `Button` components

Part of #1727

Highlights a11y (2/2) - Make highlights "visible" to screen readers

Use CSS `::before` and `::after` to add "comment start" and "commend
end" notices around highlighted text which screen readers will read but
which are not visible.

This pattern follows the example of how highlights are presented in
Google Docs and also a suggestion in a blog post from the Paciello
Group.

This will get quite audibly "noisy" if there are a lot of overlapping
highlights, but I think it is better than not having the highlights be
visible to screen reader users at all.

Highlight a11y (1/2) - Rename highlights CSS styles and move to separate module

We're renaming CSS classes to have a `hypothesis-` prefix to make it
more obvious what they are associated with, so update the selector
accordingly.

 - Remove the vestigial "annotator-" prefix for the hypothesis highlight
   CSS rules and replace with "hypothesis-".

 - Move the highlights styles to a separate module for consistency with
   the sidebar styles, where each component's styles goes in its own
   module and also to simplify the entry point (annotator.scss) module

Render `aria-selected=“false”` rather than omit the prop when tab is not selected

- Change [More/Less] button to use a <button> tag with `aria-pressed` state
- Add corresponding tests
- Change excerpt wrapper to have role=“presentation” since its meaningless for screen readers.

Fix eslint issues in HelpPanel component

Decouple `wrapReactComponent` from Angular `$injector`

The aria-selected prop shall be “true” or “false” on items in the list. Previously this was truthy so it was omitted from the DOM when false.  Undefined has a different meaning than aria-selected=“false”

Pass the service container directly to `wrapReactComponent` instead of
looking up services via Angular's `$injector` service.

This removes the need to register services with Angular if only other
services or Preact components use them. This will enable us to
incrementally remove these service registrations as the migration
continues.

As a starting point, remove the "tags" service registration, as all the
UI components and services that use it have been migrated.

Add missing effect dependencies in StreamSearchInput

Remove unnecessary registration of several classes / functions with Angular

Add `save` method to `AnnotationsService`; use it in `AnnotationOmega`

Also add polyfill for `Promise.prototype.finally`

This fixes an issue, and corresponding warning in tests, where an effect
would unnecessarily run on every render.

See https://hypothes-is.slack.com/archives/C1M8NH76X/p1581517940185900

- <a> tags without real href attributes should be converted to buttons.
- Did not use our button component in this instance because we don’t have control over the icon position relative to the text.

Bump axe-core from 3.4.1 to 3.4.2

Bump codecov from 3.6.4 to 3.6.5