This is a breaking change.

Changelog:
- TinyMCE is not prebundled externally anymore and is now treated as a normal npm dependency that will be automatically updated like any other dependency
  - Our emoji and image handling plugins are now located at src/lib/tinymce/
  - The npm module @open-xchange/tinymce is therefore of now obsolete and its use is deprecated
- Toolbar configuration has changed! Please see the official migration guide: https://www.tiny.cloud/docs/tinymce/6/migration-from-5x/
- TinyMCE skin adapts to App Suite Theme via CSS variables
- TinyMCE dialog style deviations are now remedied
- Keyboard support: Using escape to dismiss mail compose works now from TinyMCE