Merge commit '877090518682b6c77ba9bdfa0231afd56daec44d' into glitch-soc/merge-upstream

Conflicts:
- `app/models/concerns/user/has_settings.rb`:
  Not a real conflict, upstream added a setting textually close to a glitch-soc one.
  Added upstream's new setting.
- `app/views/settings/preferences/appearance/show.html.haml`:
  Not a real conflict, upstream added a setting textually close to a glitch-soc one.
  Added upstream's new setting.
- `config/routes.rb`:
  Upstream moved web app routes to `config/routes/web_app.rb`, while glitch-soc had
  an extra route.
  Moved the extra route to `config/routes/web_app.rb`.
- `spec/controllers/settings/preferences/appearance_controller_spec.rb`:
  This spec got converted to a system spec upstream.
  However, the theme setting works differently in glitch-soc, so the spec had been
  changed.
  Changed the corresponding system spec as well.

lib/sanitize_ext/sanitize_config.rb

@@ -126,7 +126,7 @@ class Sanitize
 
       add_attributes: {
         'a' => {
-          'rel' => 'nofollow noopener noreferrer',
+          'rel' => 'nofollow noopener',
           'target' => '_blank',
         },
       },
@@ -173,7 +173,7 @@ class Sanitize
       node = env[:node]
 
       rel = (node['rel'] || '').split & ['tag']
-      rel += %w(nofollow noopener noreferrer) unless TagManager.instance.local_url?(node['href'])
+      rel += %w(nofollow noopener) unless TagManager.instance.local_url?(node['href'])
 
       if rel.empty?
         node.remove_attribute('rel')