[edit] Enable document comments

[auniverseaway]

A friction point with customers who want to reduce their content creation steps is that they need comments within a DA doc if they are going to consider moving away from Google Docs / Word.

Criteria of acceptance

1. Ability to annotate pieces of content.
2. Works with ProseMirror / YJS
3. Does not get written out in a way that Helix will pick up.

Additional considerations

1. A nice to have feature would be a new role for "commenter" / "collaborator" but this is extremely nice to have.