This feature is available on Enterprise
To approve an edit:
Go to the Review tab on the Edits page of a project
Turn the Approve switch on
It will note who approved it, and what date
Note, you can also filter on only Approved content in the Library
Important note: you can only see the latest version of an Edit within the Library. This means that if you have an approved version of an Edit and you then create a new version, that original approved version will no longer be visible in the Library, please approve the new version to view in the Library when you are filtering on approved Edits.