CKEditor5 42+ Migration

[tony]

This update may take time to do: https://ckeditor.com/docs/ckeditor5/latest/updating/nim-migration/custom-plugins.html

If you require CKEditor5-Math, try to stay <42 until this is released.

[Witoso]

Just a small nitpick, you can update the editor to version 42+ and use old setups, we are continuing to support them. What you meant I think is that you can't use new installation methods. Thanks!

If you need any help during the migration, let us know :)

[luniki]

Hi @tony! Do you have a plan if and when you can work on this issue?

[eliandoran]

If it's of interest, I've updated the math plugin to support CKEditor 45 and the new plugin system.
The only downside is that it's part of a monorepo as opposed to a package, so it can be found here: https://github.com/TriliumNext/Notes/tree/develop/packages/ckeditor5-math

The tests were also converted to vitest.