debug: Set widgets' CSS names to help identifying them

It's useless for styling, but makes it much easier to identify a widget
corresponding to a particular user, room or account in the inspector :-)
1 job for wip/fmuellner/widget-names in 3 minutes and 45 seconds (queued for 3 seconds)
Status Name Job ID Coverage
  Build
passed build-polari #1295

00:03:45