A Form has a list of grammatical features to indicate the tense, case and similar features of a form. T162788 creates a basic non-editable view of these grammatical features. We now want to have them be editable as well. Each feature should be a link to an existing Wikidata item.

whiteboard mockup by @thiemowmde:

acceptance criteria:

• I can edit existing grammatical features.
• I can only select existing items as grammatical features.

Note: Entered data is not supposed to be persisted. After page reload, all changes will be gone,