Admin/Mod labels

This is part of a set of threads started after @GinnyMcQueen 's audit, cf https://governance.funkwhale.audio/d/pQS1Uznd/abuse-audit

Feature summary

Clear indication of who the Admin/Mods of a pod are.

Labeling Admins and Mods and having them listed clearly for people to contact for support makes moderation easier/more transparent.