Add Translate extension to main wiki

[Tigerfell]

There has been some discussion among the wiki editors whether to add the translate extension. @lectrician1 wrote a proposal that was subsequently accepted. Before the extension can be installed as intended, MediaWiki needs to be updated to version 1.38 (currently 1.37). I can write a PR that adds the extension.

Includes/obsoletes #555

[tomhughes]

Given how traumatic the last upgrade was I'm in no hurry to do another without some sort of guarantees that it isn't going to break everything.

[lectrician1]

Could someone look into doing this now?

[Tigerfell]

This is currently blocked by #749.

[muekoeff]

MediaWiki has been updated to 1.39 with openstreetmap/chef@bb3cefead93fa6d05987cc19801e6a87672ddf18 and #749 has been resolved. Seems like this issue is now unblocked.