Add Microsoft extensions

[freephile]

https://github.com/microsoft/MediaWiki-Extensions

[hexmode]

I was cleaning up this repo last night so I spent some time looking at the microsoft/MediaWiki-Extensions repo. It would work best if each extension could be made into its own repository. As of this writing, the only extension in the repository is the PandocUpload extension. @jeffw16 (or someone else with access to the repo) could even make the repo a container of submodules for individual extensions like the nonwmf-extensions is.

[jeffw16]

The reason I didn't make individual repos for each extension is because of the additional overhead and paperwork I'd have to fill out internally. Microsoft OSS has many policies governing open source repos.

[jeffw16]

Sadly I am currently the only active maintainer of that repo. The other co-maintainer is a coworker of mine who has graciously agreed to act as a co-sponsor of the repo, which is required for the repo to be up.