Provide summary + diff over the mkdocs rendering for PRs

[yarikoptic]

Your idea

Inspired by

• [ENH] Move PET DICOM correspondences into term definitions #2298

where we should not really see much if any difference in the .html etc rendering of the bids-specification website (besides time stamps etc). In some other, in particular while changing supplemental MACROSes etc, we would like to see/visualize the diffs on rendering, or otherwise spot potential regressions or side-effects.

Ideally there could be also annotations on the RTD PR preview renderings on the changes (e.g. a pop up which if clicked would show the diff for that paragraph or figure or ...), that would likely need to be mkdocs specific then and trickier.

Likely it would need to provide a "comment" within PR with details but I hate when they overfill the main thread in a PR, so if could somehow be

• present for each build in the history
• only the latest present as a comment with details within expandable <details/> html constructs

WDYT @effigies ?

[effigies]

This is already enabled in RTD:

[yarikoptic]

that's nice, let's consider it done, I missed that! Let's consider it done.

But it is a little odd looking though for tables as to me they look

I guess smth to report ?