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.
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Bumps [@sentry/browser](https://github.com/getsentry/sentry-javascript) from 5.27.5 to 5.27.6.
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Bumps [postcss-url](https://github.com/postcss/postcss-url) from 10.1.0 to 10.1.1.
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Bumps [terser](https://github.com/terser/terser) from 5.5.0 to 5.5.1.
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Bumps [@babel/core](https://github.com/babel/babel/tree/HEAD/packages/babel-core) from 7.12.7 to 7.12.9.
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Bumps [aws-sdk](https://github.com/aws/aws-sdk-js) from 2.792.0 to 2.799.0.
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Bumps [typescript](https://github.com/Microsoft/TypeScript) from 4.0.5 to 4.1.2.
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Bumps [prettier](https://github.com/prettier/prettier) from 2.1.2 to 2.2.0.
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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.
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Bumps [puppeteer](https://github.com/puppeteer/puppeteer) from 5.4.1 to 5.5.0.
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Bumps [terser](https://github.com/terser/terser) from 5.3.8 to 5.5.0.
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Bumps [fetch-mock](https://github.com/wheresrhys/fetch-mock) from 9.10.7 to 9.11.0.
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Bumps [axe-core](https://github.com/dequelabs/axe-core) from 4.0.2 to 4.1.1.
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Bumps [postcss](https://github.com/postcss/postcss) from 8.1.7 to 8.1.9.
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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.
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Bumps [eslint](https://github.com/eslint/eslint) from 7.13.0 to 7.14.0.
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Bumps [@babel/preset-react](https://github.com/babel/babel/tree/HEAD/packages/babel-preset-react) from 7.12.5 to 7.12.7.
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Bumps [@babel/core](https://github.com/babel/babel/tree/HEAD/packages/babel-core) from 7.12.3 to 7.12.7.
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Both are functionally equivalent in this code, but we're using `Object<K,V>`
elsewhere, so prefer that for consistency.

This doesn't serve a purpose any more since the arguments are now values
rather than promises.

Ensure that the `describe` function in `anchoring/pdf.js` fails with a
useful error if the passed range includes text outside of the PDF page's
text layer. In this case `getNodeTextLayer` will return `null` and
existing code in `describe` will throw to indicate the range starts or
ends outside of the text layer.

This will help to avoid the confusion that arose in
https://github.com/hypothesis/client/issues/1464.

This behavior is still not really useful from the end user's point of
view, but at least the error is better. Improving the actual behavior
will come later.

This has been replaced by the `TextRange.toRange` method in `text-range.js`.
The test cases are covered by the tests for `TextRange` and
`TextPosition`.

The PDF anchoring code was using several different dependencies to
to handle converting between ranges and text positions, as well as
normalizing ranges to that they start and end in text nodes.

This commit simplifies the picture by converting the PDF anchoring code
to use only the `TextRange` and `TextPosition` classes for these
purposes.

 - Change the PDF anchoring code to use the `TextRange` and
   `TextPosition` classes to handle converting a DOM range into text
   offsets in `describe`

 - Change the PDF anchoring code to use `TextRange` to handle resolving
   a (start, end) pair of character offsets within a page to a `Range`

 - Improve the type information for several related functions within the
   PDF anchoring code

Try to explain the issue with `textContent` in a better way.

`Node.textContent` has a quirk where it does not count text in comments
or processing instructions when called on an `Element` but does return
the comment / processing instruction data if called directly on a
`Comment` or `ProcessingInstruction` node.

To make conversion between `Range`s and `TextRange`s consistent in both
directions we need to always ignore text in comments/processing
instructions.