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

Conflicts:
- `README.md`:
  Our README is completely different. Discarded upstream changes.
- `app/javascript/packs/mailer.js`:
  We had removed the file. Move the changes to `app/javascript/core/mailer.js`.

app/views/layouts/admin.html.haml

@@ -7,12 +7,12 @@
       .sidebar-wrapper__inner
         .sidebar
           = link_to root_path do
-            = image_pack_tag 'logo.svg', class: 'logo', alt: 'Mastodon'
+            = render_logo
 
           .sidebar__toggle
             .sidebar__toggle__logo
               = link_to root_path do
-                = svg_logo_full
+                = logo_as_symbol(:wordmark)
 
             = link_to '#', class: 'sidebar__toggle__icon' do
               = fa_icon 'bars'