CKEditor 5 Integration

I am integrating CKEditor 5 for Angular.

I am trying to find all relevant differences to CKEditor 4.

I made a comparison here: https://github.com/dasch-swiss/dsp-ui-lib/pull/134#issuecomment-664954296

@loic.jaouen Could you please have a look? Could you provide my with some complex XML examples using the standard mapping?

EDIT webapi/_test_data/test_route/texts/StandardHTML.xml is a nice example.