Allow some customization in AnnotationTimestamps edited text

[acelaya]

Part of https://github.com/orgs/hypothesis/projects/156/views/2?pane=issue&itemId=124121878

Enhance withEditedTimestamp prop in AnnotationTimestamps component, so that it allows a variant name to be passed, customizing the "edited" text.

It still allows false and true values, which continue behaving the same (true is now equivalent to using the "default" variant).

TL;DR

This change is needed so that we can display more prominent "edited" texts in the moderation queue. I considered other options, like allowing classes to be passed, but that required an extra prop which was only relevant if withEditedTimestamp is true, or passing a list of classes to that prop, which I reckon is less intuitive than a variant name.

I also considered extracting that piece into its own component, which in turn allows classes to be provided, and let consumers compose with individual components as desired. However, the logic to render that piece is too coupled with other AnnotationTimestamps internal details, causing some duplication or having to expose too many of those details.

With that in mind I ended up with this approach, which is a bit less flexible, but very simple. We can add more variants in future if needed.

[acelaya]

I decided to just test with a data-variant attribute, rather than testing the actual classes being added for every variant, to reduce coupling the test with implementation details.

[acelaya]

I'm not super happy with these variant names. I'm open to suggestions.

[robertknight]

The intent is clear from the names, so they will work as a starting point. If you need to add more variants in future it will become clearer how to distinguish them.

[acelaya]

Ok!