Add more extensive Tiptap v3-specific functionality and optimizations

[sjdemartini]

Picking up from #335, handling part (2) mentioned here:

Based on the migration docs, it sounds like much of this could work out of the box in Tiptap v3, but to take real advantage of the capabilities of v3 (such as render performance with shouldRerenderOnTransaction/useEditorState), this will require a bit more effort to do well and may require some breaking changes that aren't compatible with v2.

I'll look into:

1. Supporting v3 in a basic way soon, and then
2. Explore what a more full-featured approach would take

In addition later for v3, per some other notes in https://tiptap.dev/blog/release-notes/tiptap-3-0-is-stable as well, it would be nice to:

1. Give the demo a facelift and ensure it works well (e.g. use Floating UI for mentions instead of Tippy)
2. Likely remove the mui-tiptap FontSize extension in favor of Tiptap's new extension
3. Support new extensions with dedicated mui-tiptap components where it's useful:
   a. Emoji
   b. File Handling
   c. Others?

Originally posted by @sjdemartini in #335