Click recording://entity/path links in markdown

[emilk]

What

You can now embed links to entities in markdown documents using recording://entity/path, and link to components using recording://entity/path.Color.

In order to support this, a new DataPath is introduced, with a stricter parsing of entity paths. Previously foo bar was a valid path, but now you are only allowed ASCII, numbers, underscore and dash as names (outside of quotes).

A (uncompleted) description of the SfM example as markdown to

• Test how that feels as documentation
• Try out the ability to link directly to entities and components from within the markdown

Checklist

• I have read and agree to Contributor Guide and the Code of Conduct
• I've included a screenshot or gif (if applicable)
• I have tested demo.rerun.io (if applicable)

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[emilk]

Already reviewed in #3389