MobileFrontend uses Doxygen to generate PHP documentation on https://doc.wikimedia.org/ which can be quite useful for everyone. Since Popups and Vector have preexisting documentation and the latter is entering heavy development, it seems reasonable that the effort to publish this documentation be made.
- Copy [[ https://gerrit.wikimedia.org/g/mediawiki/extensions/MobileFrontend/+/b593da502/Doxyfile | MobileFrontend uses Doxygen to generate PHP documentation ]] to Vector and Popups and make revisions as wanted.
- Add post-merge CI jobs for Vector and Popups. This appears to be just [[ https://gerrit.wikimedia.org/r/plugins/gitiles/integration/config/+/39e935c/zuul/layout.yaml#3858 | adding `- mwext-doxygen-publish` ]].
== Acceptance criteria
 PHP documentation for Vector and Popups appears on https://doc.wikimedia.org/.
 MobileFrontend's Doxyfile is opportunistically updated as wanted.
Documentation-only change so no testing needed.