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.

Add an option that enables the embedder to configure a content
provider/partner banner to be shown in the client, indicating who is
providing the content.

Add an option to show a banner at the top of the PDF viewer indicating
where the content came from. This is a contractual requirement for
working with certain content providers.

Listen for mouseup/mousedown events on the document body rather than document
itself, so that we can still capture them if an event listener on
`document.body` or `document.documentElement` stops propagation of the event.
The VitalSource integration does this for example to prevent VitalSource's own
selection UI appearing, but ordinary web pages could do something similar.

In VitalSource books, this change makes the adder behave the same as it does in
HTML and PDF documents where, when making a selection with the mouse, the adder
only appears when the mouse is released so it doesn't get in the way during the
selection.

While updating the tests for this change, they were converted to use a real
document, as the complexity of mocking the relevant parts of the DOM document
interface accurately is now too high.

Bumps [katex](https://github.com/KaTeX/KaTeX) from 0.15.2 to 0.15.3.
- [Release notes](https://github.com/KaTeX/KaTeX/releases)
- [Changelog](https://github.com/KaTeX/KaTeX/blob/main/CHANGELOG.md)
- [Commits](https://github.com/KaTeX/KaTeX/compare/v0.15.2...v0.15.3)

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Bumps [karma-chrome-launcher](https://github.com/karma-runner/karma-chrome-launcher) from 3.1.0 to 3.1.1.
- [Release notes](https://github.com/karma-runner/karma-chrome-launcher/releases)
- [Changelog](https://github.com/karma-runner/karma-chrome-launcher/blob/master/CHANGELOG.md)
- [Commits](https://github.com/karma-runner/karma-chrome-launcher/compare/v3.1.0...v3.1.1)

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updated-dependencies:
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  dependency-type: direct:development
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Bumps [eslint](https://github.com/eslint/eslint) from 8.10.0 to 8.11.0.
- [Release notes](https://github.com/eslint/eslint/releases)
- [Changelog](https://github.com/eslint/eslint/blob/main/CHANGELOG.md)
- [Commits](https://github.com/eslint/eslint/compare/v8.10.0...v8.11.0)

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- dependency-name: eslint
  dependency-type: direct:development
  update-type: version-update:semver-minor
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Bumps [puppeteer](https://github.com/puppeteer/puppeteer) from 13.5.0 to 13.5.1.
- [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/v13.5.0...v13.5.1)

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  dependency-type: direct:development
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Bumps [@sentry/browser](https://github.com/getsentry/sentry-javascript) from 6.18.1 to 6.18.2.
- [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/6.18.1...6.18.2)

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- dependency-name: "@sentry/browser"
  dependency-type: direct:development
  update-type: version-update:semver-patch
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Bumps [aws-sdk](https://github.com/aws/aws-sdk-js) from 2.1088.0 to 2.1092.0.
- [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/v2.1088.0...v2.1092.0)

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- dependency-name: aws-sdk
  dependency-type: direct:development
  update-type: version-update:semver-minor
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Bumps [showdown](https://github.com/showdownjs/showdown) from 2.0.2 to 2.0.3.
- [Release notes](https://github.com/showdownjs/showdown/releases)
- [Changelog](https://github.com/showdownjs/showdown/blob/2.0.3/CHANGELOG.md)
- [Commits](https://github.com/showdownjs/showdown/compare/2.0.2...2.0.3)

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- dependency-name: showdown
  dependency-type: direct:development
  update-type: version-update:semver-patch
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Bumps [mocha](https://github.com/mochajs/mocha) from 9.2.1 to 9.2.2.
- [Release notes](https://github.com/mochajs/mocha/releases)
- [Changelog](https://github.com/mochajs/mocha/blob/master/CHANGELOG.md)
- [Commits](https://github.com/mochajs/mocha/compare/v9.2.1...v9.2.2)

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  dependency-type: direct:development
  update-type: version-update:semver-patch
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Bumps [eslint-plugin-react](https://github.com/yannickcr/eslint-plugin-react) from 7.29.3 to 7.29.4.
- [Release notes](https://github.com/yannickcr/eslint-plugin-react/releases)
- [Changelog](https://github.com/yannickcr/eslint-plugin-react/blob/master/CHANGELOG.md)
- [Commits](https://github.com/yannickcr/eslint-plugin-react/compare/v7.29.3...v7.29.4)

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- dependency-name: eslint-plugin-react
  dependency-type: direct:development
  update-type: version-update:semver-patch
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Bumps [rollup](https://github.com/rollup/rollup) from 2.70.0 to 2.70.1.
- [Release notes](https://github.com/rollup/rollup/releases)
- [Changelog](https://github.com/rollup/rollup/blob/master/CHANGELOG.md)
- [Commits](https://github.com/rollup/rollup/compare/v2.70.0...v2.70.1)

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  dependency-type: direct:development
  update-type: version-update:semver-patch
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When choosing a scroll anchor to preserve the visible content after toggling
side-by-side mode, ignore content in elements with `position: fixed` or
`position: sticky` styles, since this content won't significantly shift its
position as a result of the document content being resized.

`waitFor` has a short default timeout of 10ms and this test sometimes
failed in CI. Try increasing it to reduce flakiness. We might want to
consider changing the `waitFor` default in future, although we also want
to encourage test authors to avoid writing tests that frequently wait
for long (> 10ms) periods of time.