Merge branch 'master' into glitch-soc/master

Conflicts:
- `README.md`:
  We have different README files. Discarded upstream changes.
- `app/views/layouts/admin.html.haml`:
  Conflict due to glitch-soc theming system.
  Adapted upstream changes.
- `app/views/layouts/embedded.html.haml`:
  Conflict due to glitch-soc theming system.
  Adapted upstream changes.
- `yarn.lock`:
  No real conflict, glitch-specific dependency too close to
  an updated one. Adapted upstream change.

app/controllers/api/oembed_controller.rb

@@ -3,6 +3,8 @@
 class Api::OEmbedController < Api::BaseController
   respond_to :json
 
+  skip_before_action :require_authenticated_user!
+
   def show
     @status = status_finder.status
     render json: @status, serializer: OEmbedSerializer, width: maxwidth_or_default, height: maxheight_or_default