DEV: introduces tippy (PR #15409)

Having a good tooltip js library is kinda mandatory nowadays. We already use popper, tippy is built on top of it and should include all the features we need, just as popper, it’s very much extensible if needed.

The size is rather limited once compressed and will also allow us to remove significant amount of code in footnote plugin for example (and avoid in the future).

GitHub

very supportive of a change here, but timing is not great needs to wait a few weeks for 2.9

@jjaffeux also looks like it needs a rebase.

yes agreed, will move this to draft for now