Merge branch 'master' into glitch-soc/merge-upstream

Conflicts:
	app/controllers/application_controller.rb

Changed instance theme selection by instance flavour selection.

app/controllers/admin/settings_controller.rb

@@ -16,6 +16,8 @@ module Admin
       timeline_preview
       show_staff_badge
       bootstrap_timeline_accounts
+      flavour
+      skin
       thumbnail
       hero
       min_invite_role
@@ -23,6 +25,7 @@ module Admin
       peers_api_enabled
       show_known_fediverse_at_about_page
       preview_sensitive_media
+      custom_css
     ).freeze
 
     BOOLEAN_SETTINGS = %w(