Reason:
i18n error messages have been broken for three years ( T199033 ). It barely got any code update and wikiapiary only find a single wiki using it.
- Archive documentation on mediawiki.org https://www.mediawiki.org/wiki/Extension:Transliterator
- Remove from mediawiki/extensions (along with in .gitmodules)
- Remove tests in integration/config (zuul/layout.yaml)
- Remove from translatewiki (groups/MediaWiki/mediawiki-extensions.txt)
- Empty repository and add a OBSOLETE file.
- Archive Phabricator project MediaWiki-extensions-Transliterator for associated extension/skin
- Edit Phabricator project MediaWiki-extensions-Transliterator description for associated extension/skin with a link to this ticket
- Archive the extension's diffusion repository: rETRX
- Mark the repository read-only in Gerrit: https://gerrit.wikimedia.org/r/#/admin/projects/mediawiki/extensions/Transliterator
- Delete the GitHub mirror: https://github.com/wikimedia/mediawiki-extensions-Transliterator