Feature: Approval of edits

[MaximilianKindshofer]

Describe the feature you'd like
I would like a feature for the approval of edits by the owner of a page

Describe the benefits this feature would bring to BookStack users
A viewer could purpose changes to a page or chapter e.g. spelling or even adding a new section an collaborate on a book with the author / owner

[ssddanbrown]

Thanks for the request @MaximilianKindshofer. I'm going to close this off since I see a lot of logical overlap with #473.