CKEditor 5 - Upgrade feature

[salem84]

Hi, I'm creating a custom editor to use CKEditor 5 in a side project of mine.
Let me know if this feature could be useful for the project, so I could create a fork of main project and update scripts (in Serenity.Assets) and HtmlContentEditor.

[VictorTomaili]

Hi @salem84
Pull requests are welcome, we will review your code and merge after everything is ok.

[volkanceylan]

CKEditor 5 license is not compatible with ours.