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

Conflicts:
- app/controllers/accounts_controller.rb
- app/controllers/follower_accounts_controller.rb
- app/controllers/statuses_controller.rb

All conflicts caused by the additional `use_pack` used for glitch-soc's theming
system.

app/controllers/application_controller.rb

@@ -227,6 +227,11 @@ class ApplicationController < ActionController::Base
     response.headers['Vary'] = 'Accept'
   end
 
+  def mark_cacheable!
+    skip_session!
+    expires_in 0, public: true
+  end
+
   def skip_session!
     request.session_options[:skip] = true
   end