Namespace annotations module

Namespace viewer module

Add `aria-label` to annotation tags

Add an `aria-label` as a first-stop step to better a11y on annotation
tags.

Hide inaccurate annotation counts when in user-focused mode

- Do not render the count of annotations or notes that will be visible
  if a selection-mode filter is cleared when also in user-focused mode,
  as this number is inaccurate.
- Refactor component and tests to make different “modes” more codified

Whitelist Sentry error reports to only include errors from our code

Add docs for building the docs locally

Standardize the module test descriptions

Namespace session and groups modules

This adds documentation for how to build the docs locally.

Previously the `make docs` command required you to have Python 3 and tox
installed system-wide, neither of which are required for any of our
other projects anymore, and this wasn't documented anywhere.

This PR changes `make docs` to use pyenv to install Python 3 and tox, as
all our other Python projects do, and adds a Building the Docs Locally
page to the docs with instructions on how to install pyenv and build the
docs locally.

pyenv and tox are _not_ added to the general client dev install
instructions since they're only needed to build the docs.

Bump aws-sdk from 2.517.0 to 2.521.0

Bump @sentry/browser from 5.6.2 to 5.6.3

To reduce noise from Sentry, filter events to exclude all errors which
cannot be attributed to our code based on the URLs in the error's stack
trace.

This will prevent us from receiving reports caused by eg. script tags
injected by browser extensions or custom browsers.

There is a downside to this: We will stop receiving error reports which
are caused by / occur in our code but cannot be attributed to it. This
can happen for example if a promise is rejected with a non-Error value
so no stack trace can be obtained.

For the moment, we're prioritising precision (% of error reports
actually caused by problems in our code) over recall (% of problems in
our code that are reported).

Bump karma from 4.2.0 to 4.3.0

Bump commander from 3.0.0 to 3.0.1

Bump cross-env from 5.2.0 to 5.2.1

Bump chance from 1.0.18 to 1.1.0

Bump sinon from 7.4.1 to 7.4.2

Bumps [@sentry/browser](https://github.com/getsentry/sentry-javascript) from 5.6.2 to 5.6.3.
- [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/5.6.2...5.6.3)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Bumps [eslint](https://github.com/eslint/eslint) from 6.2.2 to 6.3.0.
- [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/v6.2.2...v6.3.0)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Bumps [aws-sdk](https://github.com/aws/aws-sdk-js) from 2.517.0 to 2.521.0.
- [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/v2.517.0...v2.521.0)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Bumps [sinon](https://github.com/sinonjs/sinon) from 7.4.1 to 7.4.2.
- [Release notes](https://github.com/sinonjs/sinon/releases)
- [Changelog](https://github.com/sinonjs/sinon/blob/master/CHANGELOG.md)
- [Commits](https://github.com/sinonjs/sinon/compare/v7.4.1...v7.4.2)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Bumps [chance](https://github.com/chancejs/chancejs) from 1.0.18 to 1.1.0.
- [Release notes](https://github.com/chancejs/chancejs/releases)
- [Commits](https://github.com/chancejs/chancejs/commits)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Bumps [cross-env](https://github.com/kentcdodds/cross-env) from 5.2.0 to 5.2.1.
- [Release notes](https://github.com/kentcdodds/cross-env/releases)
- [Changelog](https://github.com/kentcdodds/cross-env/blob/master/CHANGELOG.md)
- [Commits](https://github.com/kentcdodds/cross-env/compare/v5.2.0...v5.2.1)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Bumps [commander](https://github.com/tj/commander.js) from 3.0.0 to 3.0.1.
- [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/v3.0.0...v3.0.1)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Bumps [karma](https://github.com/karma-runner/karma) from 4.2.0 to 4.3.0.
- [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/v4.2.0...v4.3.0)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Add custom serialization for `Event` exception values in Sentry reporting

Add annotation counts and iterate on UX for user-focused mode

Add annotation counts in user-focused mode and tweak UX for clarity

Record document URL as "extra" metadata rather than a tag

It turns out that Sentry has various contraints on the characters that
can appear in tags as well as their length. For debugging purposes we
want to capture the full document URL unmodified. Therefore capture this
as un-indexed "extra" metadata, which has fewer constraints, rather than
an indexed "tag".

To help debug https://sentry.io/organizations/hypothesis/issues/1190575523
and similar issues, add logic to extract details of uncaught thrown
`Event`s and attach them to Sentry reports.

Do not link last-edited timestamp to annotation single view