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

Conflicts:
- app/models/media_attachment.rb
  Upstream added audio attachment support
- app/serializers/initial_state_serializer.rb
  Upstream added audio attachment support and how mimetypes are returned
- app/serializers/rest/instance_serializer.rb
  Upstream added a few fields
- config/application.rb
  Upstream added a different paperclip transcoder

app/javascript/mastodon/locales/defaultMessages.json

@@ -1051,7 +1051,7 @@
   {
     "descriptors": [
       {
-        "defaultMessage": "Add media (JPEG, PNG, GIF, WebM, MP4, MOV)",
+        "defaultMessage": "Add media ({formats})",
         "id": "upload_button.label"
       }
     ],