Add the ability to rollback the change currently shown on the page

- Currently the rollback summary is set to the default from the API:
  `Reverted edits by [[Special:Contributions/Username|Username]] ([[User
    talk:Username|Talk]]); changed back to last version by
    [[User:PreviousEditor|PreviousEditor]]`
- Handle any errors such as invalid tokens, or no user specified.
- Once vandalism is rolled back, load the next revision.