Compatibility with CKEditor5

I got a great part working of it (not a complete solution yet), but because Entity Embed is not yet compatible I'm going to put my work on hold because at the moment it's too buggy.

Committed all my work on request to an issue fork. Note that it's a very heavy draft, no where near finished. It's also not fully working yet.

I created a separate module which integrates entity browser with ckeditor 5, without any linkit dependency:
https://www.drupal.org/project/ckeditor5_entity_browser →