Fix embedded player

(broken because I forgot to adapt it to glitch-soc's theming system)

app/controllers/media_controller.rb

@@ -11,6 +11,7 @@ class MediaController < ApplicationController
   before_action :verify_permitted_status!
   before_action :check_playable, only: :player
   before_action :allow_iframing, only: :player
+  before_action :set_pack, only: :player
 
   content_security_policy only: :player do |p|
     p.frame_ancestors(false)
@@ -43,4 +44,8 @@ class MediaController < ApplicationController
   def allow_iframing
     response.headers['X-Frame-Options'] = 'ALLOWALL'
   end
+
+  def set_pack
+    use_pack 'public'
+  end
 end