Create and implement annotations in the content profile

Submitting an initial PR for annotations in the UI as it might benefit from an extra set of eyes. There are a few quirks here and there while using the annotator which still need to be ironed out.

Document preview widget:
- Added annotation button to toggle the annotation sidebar
- Restructuring to allow for Sidebar to stick to the side of the document viewer

Custom sidebar plugin:
- Create annotations
- Delete annotations
- Edit annotations
- Reply to annotations

Activities:
- Activity added to the list when a document has been annotated