**Reason**
AddThis service is shutting down on May 31, 2023.
(This task isn't really actionable until then but I'm creating it now given the current slow rate of people processing extension archivals)
**To-do list**
- This task
-- [X] Add maintainers of that extension as subscribers to this task (if they have no apparent Phabricator account, notify them on-wiki or via email if possible and note it here).
-- [X] Add Phabricator project <#ProjectX> as a tag for this task, and remove #mediawiki-extensions-other as appropriate.
- On-wiki documentation
-- [ ] Archive documentation on `mediawiki.org` (https://www.mediawiki.org/wiki/Extension:AddThis): replace page contents with `{{Archived extension|last revision id before archiving|task=T335463}}`;
-- [ ] Remove `<translate>`, visit Special:PageTranslation, and click "remove from translation" (if you don't have the translation administrator right, ask a [[ https://www.mediawiki.org/wiki/Special:ListUsers/translationadmin | user who does ]]).
-- [ ] Update Wikidata item (https://www.wikidata.org/wiki/Q21676147) associated with documentation page
--- [ ] add statement `Abandonware (Q281039)` to `instance of (P31)` together with qualifier `start time (P580)` = the YYYY-MM-DD date that you decided to archive extension (generally per edit history)
--- [ ] add qualifier `end time (P582)` = the YYYY-MM-DD (same date as above) to `instance of (P31) = MediaWiki extension (Q6805426)`
- Phabricator
-- [ ] Mark all Phabricator tasks for the extension either Declined or Invalid. Add a comment pointing to this task when doing so for reference.
- Translatewiki.net/translations
-- [ ] Remove from `translatewiki.net` ([[ https://gerrit.wikimedia.org/r/plugins/gitiles/translatewiki/+/refs/heads/master/groups/MediaWiki/mediawiki-extensions.txt | groups/MediaWiki/mediawiki-extensions.txt ]]).
- Configuration/tests/integrations/etc.
-- [ ] Remove tests in [[ https://gerrit.wikimedia.org/g/integration/config | integration/config ]] ([[ https://gerrit.wikimedia.org/r/plugins/gitiles/integration/config/+/master/zuul/layout.yaml | zuul/layout.yaml ]]).
- Repositories
-- [ ] Empty repository, leaving only the README indicating the repo is archived, and referring to this task by URL.
-- [ ] Remove from [[ https://gerrit.wikimedia.org/r/plugins/gitiles/mediawiki/extensions/+/master | mediawiki/extensions ]] (along with in `.gitmodules`).
-- [ ] Mark the repository read-only in Gerrit (also edit description to prepend "[ARCHIVED]" and a reference to this task): (https://gerrit.wikimedia.org/g/mediawiki/extensions/AddThis).
-- [ ] Archive the Diffusion repository for the extension: (rEADT).
-- [ ] Delete the GitHub mirror: (https://github.com/wikimedia/mediawiki-extensions-AddThis).