Wiki page events webhook should include Wiki attributes (url, repo, etc)
This issue follows the patch to enable Webhook through the Admin UI on a project (#17506 (closed)).
The hook data we are sending is not 100% correct (we send details of the project, but should also send details of the "ProjectWiki" attributes like URLs and repositories relative to the wiki itself).
We should also fix the documentation the match new hook attributes.
This will help create a future system_hook for wiki updates that will be used by Geo (gitlab-org/gitlab-ee#76)