This feature is now enabled by default.

Per discussion on the PR, it is preferable to put markup and JS in the
dev server in external files rather than as string literals in
`serve-dev.js`. This enables them to be edited without having to restart
the dev server.

 - Extract shared functions for loading and unloading client into
   `scripts/util.js`

 - Move logic specific to the index template into `scripts/index.js`.

Adding a custom attribute without a `data-` prefix could potentially
cause headaches for publishers running their code through HTML
validation tools.

The toggle button only exists on the index page. Also I fixed an issue
where an incorrect variable name went unnoticed due to DOM element IDs
creating global variables (sigh).

Add a button to the dev server to facilitate easy testing of unloading
and re-loading the client, as done by the browser extension and also
some third-party pages.

Ensure that all links, script and stylesheet elements added to the page
by the boot script are removed when the client is unloaded.

This fixes a problem where the recently added `<link>` for the notebook
app was not removed when the page was unloaded, causing attempts to
activate the browser extension on a page where the client had previously
been loaded and then removed, to fail.

The implementation works by tagging all elements with a
`hypothesis-asset` attribute in the boot script and then removing these
elements when the client is unloaded.

On mobile devices, reseting the zoom level (pinch gesture) leaves a one pixel gap between the bucket-bar and the iframe. By adding one extra pixel to the width of the bucket-bar we eliminate this issue.

Add a pressure valve to keep from loading too many annotations in groups
that have a large number of annotations.

Replace iframe in `Notebook` if `groupId` changes

`load` was written with `SidebarView` in mind, assuming the presence
of both a `groupId` and one or more `uris`. This allows the loading of
all annotations that pertain to a specific group on one or more
specific document URIs.

For Notebook, we'd like to be able to, initially, load all annotations
for a `group` but for all document URIs.

Make `load` take `options` instead of individual search arguments. Leave
requirement for a `groupId` in place for now.

Bumps [postcss](https://github.com/postcss/postcss) from 8.1.9 to 8.1.10.
- [Release notes](https://github.com/postcss/postcss/releases)
- [Changelog](https://github.com/postcss/postcss/blob/master/CHANGELOG.md)
- [Commits](https://github.com/postcss/postcss/compare/8.1.9...8.1.10)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Bumps [prettier](https://github.com/prettier/prettier) from 2.2.0 to 2.2.1.
- [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/2.2.0...2.2.1)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Bumps [autoprefixer](https://github.com/postcss/autoprefixer) from 10.0.2 to 10.0.4.
- [Release notes](https://github.com/postcss/autoprefixer/releases)
- [Changelog](https://github.com/postcss/autoprefixer/blob/master/CHANGELOG.md)
- [Commits](https://github.com/postcss/autoprefixer/compare/10.0.2...10.0.4)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

This is part of changing the annotator code to use a single
well-tested/debugged/optimized etc. implementation of Range <-> text offset
conversion in all places.

This will be useful for switching the position selector anchoring code to use the
`TextRange` class. The one place where a non-Element node was passed was
from `anchoring/pdf.js`, a context where we can easily create a dummy
element.

Bumps [core-js](https://github.com/zloirock/core-js) from 3.7.0 to 3.8.0.
- [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/v3.7.0...v3.8.0)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Bumps [@sentry/browser](https://github.com/getsentry/sentry-javascript) from 5.27.5 to 5.27.6.
- [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/5.27.5...5.27.6)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Bumps [postcss-url](https://github.com/postcss/postcss-url) from 10.1.0 to 10.1.1.
- [Release notes](https://github.com/postcss/postcss-url/releases)
- [Changelog](https://github.com/postcss/postcss-url/blob/master/CHANGELOG.md)
- [Commits](https://github.com/postcss/postcss-url/compare/10.1.0...10.1.1)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Bumps [terser](https://github.com/terser/terser) from 5.5.0 to 5.5.1.
- [Release notes](https://github.com/terser/terser/releases)
- [Changelog](https://github.com/terser/terser/blob/master/CHANGELOG.md)
- [Commits](https://github.com/terser/terser/compare/v5.5.0...v5.5.1)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Bumps [@babel/core](https://github.com/babel/babel/tree/HEAD/packages/babel-core) from 7.12.7 to 7.12.9.
- [Release notes](https://github.com/babel/babel/releases)
- [Changelog](https://github.com/babel/babel/blob/main/CHANGELOG.md)
- [Commits](https://github.com/babel/babel/commits/v7.12.9/packages/babel-core)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Bumps [aws-sdk](https://github.com/aws/aws-sdk-js) from 2.792.0 to 2.799.0.
- [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/v2.792.0...v2.799.0)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Bumps [typescript](https://github.com/Microsoft/TypeScript) from 4.0.5 to 4.1.2.
- [Release notes](https://github.com/Microsoft/TypeScript/releases)
- [Commits](https://github.com/Microsoft/TypeScript/compare/v4.0.5...v4.1.2)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Bumps [prettier](https://github.com/prettier/prettier) from 2.1.2 to 2.2.0.
- [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/2.1.2...2.2.0)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

On mobile device `@media (pointer: coarse)` is active which make the buttons larger, including those in the `annotator-toolbar`.

By making the sidebar smaller we avoid cropping the buttons outside the screen.

On mobile screen sizes, buttons get a minimum recommended size (following Apple's Human Interface Guidelines). To accomodate for that, `top-bar` height and `annotator-toobar` width needs to be adjusted accordingly.

Bumps [@sentry/browser](https://github.com/getsentry/sentry-javascript) from 5.27.4 to 5.27.5.
- [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/5.27.4...5.27.5)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Bumps [puppeteer](https://github.com/puppeteer/puppeteer) from 5.4.1 to 5.5.0.
- [Release notes](https://github.com/puppeteer/puppeteer/releases)
- [Changelog](https://github.com/puppeteer/puppeteer/blob/main/CHANGELOG.md)
- [Commits](https://github.com/puppeteer/puppeteer/compare/v5.4.1...v5.5.0)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Bumps [terser](https://github.com/terser/terser) from 5.3.8 to 5.5.0.
- [Release notes](https://github.com/terser/terser/releases)
- [Changelog](https://github.com/terser/terser/blob/master/CHANGELOG.md)
- [Commits](https://github.com/terser/terser/compare/v5.3.8...v5.5.0)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Bumps [fetch-mock](https://github.com/wheresrhys/fetch-mock) from 9.10.7 to 9.11.0.
- [Release notes](https://github.com/wheresrhys/fetch-mock/releases)
- [Commits](https://github.com/wheresrhys/fetch-mock/compare/v9.10.7...v9.11.0)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Bumps [axe-core](https://github.com/dequelabs/axe-core) from 4.0.2 to 4.1.1.
- [Release notes](https://github.com/dequelabs/axe-core/releases)
- [Changelog](https://github.com/dequelabs/axe-core/blob/develop/CHANGELOG.md)
- [Commits](https://github.com/dequelabs/axe-core/compare/v4.0.2...v4.1.1)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Bumps [postcss](https://github.com/postcss/postcss) from 8.1.7 to 8.1.9.
- [Release notes](https://github.com/postcss/postcss/releases)
- [Changelog](https://github.com/postcss/postcss/blob/master/CHANGELOG.md)
- [Commits](https://github.com/postcss/postcss/compare/8.1.7...8.1.9)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

This name better describes this component's role.

Bumps [@babel/preset-env](https://github.com/babel/babel/tree/HEAD/packages/babel-preset-env) from 7.12.1 to 7.12.7.
- [Release notes](https://github.com/babel/babel/releases)
- [Changelog](https://github.com/babel/babel/blob/main/CHANGELOG.md)
- [Commits](https://github.com/babel/babel/commits/v7.12.7/packages/babel-preset-env)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>