Reason: Per T196429#4274031.
- Archive documentation on mediawiki.org - https://www.mediawiki.org/wiki/Extension:CustomPage (diff)
- Remove from mediawiki/extensions / mediawiki/skins ( along with in .gitmodules)
- Remove tests in integration/config ( zuul/layout.yaml )
- Remove from translatewiki ( groups/MediaWiki/mediawiki-extensions.txt / groups/MediaWiki/mediawiki-skins.txt )
- Empty repository and add a OBSOLETE file.
- Archive the extension's diffusion repository: rECSP
- Mark the repository read-only in Gerrit:
- Delete the GitHub mirror: https://github.com/wikimedia/mediawiki-extensions-CustomPage