This pattern makes it clearer that we are testing for a callback not
being invoked after a sequence of events.

Fix various issues that could cause the callback to `onDocumentReady` to
fire after the subscription had been canceled.

 - `pollOnUnload` was called twice for the initial document, once at the
   top level of the function and once by the first call to
   `checkForDocumentChange`. This resulted into "unload" listeners being
   added for the same window.

 - The initial async `checkForDocumentChange` call would still fire if
   the subscription was immediately canceled

 - If the current window's "unload" event fired after the subscription
   was canceled, polling would be restarted, effectively re-subscribing
   to document changes.

Add and improve types in src/sidebar/config/ so that this directory
typechecks with `noImplicitAny` enabled.

 - Add "$rpc:requestGroups" as a possible value for the `groups` config
   in types/config.js, which code in sidebar/config/ needs to replace
   with a promise for a list of groups.

   This required a change in `sidebar/services/groups.js` to either
   check for or explicitly assert that `service.groups` is an array at
   this point (and not the string "$rpc:requestGroups").

 - Replace various `object` types with `ConfigFromHost`,
   `ConfigFromSidebar` or `SidebarSettings` as appropriate

 - Rewrite the code at the bottom of `hostPageConfig` that copies
   configuration from the `config=` URL fragment into a sanitized
   `ConfigFromHost` object, so that it is easier to read and add types
   to.

Bumps [autoprefixer](https://github.com/postcss/autoprefixer) from 10.4.2 to 10.4.4.
- [Release notes](https://github.com/postcss/autoprefixer/releases)
- [Changelog](https://github.com/postcss/autoprefixer/blob/main/CHANGELOG.md)
- [Commits](https://github.com/postcss/autoprefixer/compare/10.4.2...10.4.4)

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updated-dependencies:
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  dependency-type: direct:development
  update-type: version-update:semver-patch
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Bumps [@sentry/cli](https://github.com/getsentry/sentry-cli) from 1.73.2 to 1.74.2.
- [Release notes](https://github.com/getsentry/sentry-cli/releases)
- [Changelog](https://github.com/getsentry/sentry-cli/blob/master/CHANGELOG.md)
- [Commits](https://github.com/getsentry/sentry-cli/compare/1.73.2...1.74.2)

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updated-dependencies:
- dependency-name: "@sentry/cli"
  dependency-type: direct:development
  update-type: version-update:semver-minor
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Bumps [postcss](https://github.com/postcss/postcss) from 8.4.8 to 8.4.12.
- [Release notes](https://github.com/postcss/postcss/releases)
- [Changelog](https://github.com/postcss/postcss/blob/main/CHANGELOG.md)
- [Commits](https://github.com/postcss/postcss/compare/8.4.8...8.4.12)

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- dependency-name: postcss
  dependency-type: direct:development
  update-type: version-update:semver-patch
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Bumps [@babel/core](https://github.com/babel/babel/tree/HEAD/packages/babel-core) from 7.17.5 to 7.17.8.
- [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/v7.17.8/packages/babel-core)

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  dependency-type: direct:development
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Bumps [commander](https://github.com/tj/commander.js) from 9.0.0 to 9.1.0.
- [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/v9.0.0...v9.1.0)

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  dependency-type: direct:development
  update-type: version-update:semver-minor
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Bumps [prettier](https://github.com/prettier/prettier) from 2.5.1 to 2.6.0.
- [Release notes](https://github.com/prettier/prettier/releases)
- [Changelog](https://github.com/prettier/prettier/blob/main/CHANGELOG.md)
- [Commits](https://github.com/prettier/prettier/compare/2.5.1...2.6.0)

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- dependency-name: prettier
  dependency-type: direct:development
  update-type: version-update:semver-minor
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Bumps [aws-sdk](https://github.com/aws/aws-sdk-js) from 2.1092.0 to 2.1096.0.
- [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/v2.1092.0...v2.1096.0)

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Prevent body from jumping right in cases where `margin: auto` is set on
the body. Body may move left to make room for sidebar, but should never
move to the right.

Fixes #4280

Revert the mousedown propagation change from e70287cf.
In order to prevent VitalSource's own text selection highlight from
appearing, it is necessary to stop propagation of both mouseup and
mousedown events.

In the context of our LMS app, this banner is displayed inside a nested
iframe, so it is important to open the link in a new tab.

Use the term `charBoxes` consistently within the file and to avoid
confusion with the `text` parameter.

The name was out of place in this module and it was unused.

Previously the text layer in VitalSource PDFs consisted of a set of
absolutely positioned elements, one per word. When the user was making a
text selection and the cursor was between words, the browser could not
determine an appropriate caret position in the text. As a result text
selection was tricky.

Improve this by re-implementing ImageTextLayer to produce a more
structured DOM tree. Group the characters into words, lines and columns.
Words are laid out using inline layout into `<hypothesis-text-line>`
elements, which are then arranged using block layouts into
`<hypothesis-text-column>` elements. Columns are absolutely positioned.
Within lines and columns the gaps between words and lines are fine-tuned
using margins. This use of inline and block layouts allows the browser
to set the selection correctly when the cursor is between words or
lines. The visual gap between selected words has also been eliminated by
adding inter-word spaces to the previous word.

 - Separate page layout analysis from DOM construction. This makes these
   elements easier to understand and improve.

 - Change DOM structure generated by `ImageTextLayer` to a hierarchical
   structure of words, lines and columns.

 - Change ImageTextLayer to use DOMRect and DOMPoint as the types for
   rect and point structs. This allows sharing of geometry utilities
   with other code.

 - Simplify rescaling of text layer when image size changes by
   expressing all margins, sizes and scales in the text layer in terms
   of CSS variables (`--x-scale` and `--y-scale`) defined on the root
   `<hypothesis-text-layer>` element. When the image is resized, these
   variables are simply updated to reflect the new image size.

Add a test page at http://localhost:3000/pdf/jstor that shows the JSTOR
content banner.

Add the ability to specify custom configuration for a PDF test case by
putting the configuration in a `<basename>.config.json` file alongside
the PDF, where `<basename>` is the name of the PDF file minus the '.pdf'
extension.