Per discussion on T186670, archive teh repo!
- Archive documentation on mediawiki.org. (none apparently)
- Remove from mediawiki/extensions.
- Remove tests in integration/config.
- Remove from translatewiki.
- Remove manifest/other references from mediawiki/vagrant if they exist.
- Empty repository and add a OBSOLETE file.
- Archive Phabricator project for associated extension/skin.
- Edit Phabricator project description for associated extension/skin with a link to this ticket.
- Archive the extension's diffusion repository.
- Mark the repository read-only in Gerrit.
- Delete the GitHub mirror.