Objective

Provide the history of changes made to a page, view differences and allow to revert to a previous version.

### Tasks
- [ ] Store previous versions of a page on edit
- [ ] View a list of previous versions of a page
- [ ] Compare between 2 versions (diff view)
- [ ] View the rendered view of a previous version
- [ ] Download a specific version
- [ ] Revert to a previous version

Related to #6557