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

Conflicts:
- `app/models/account.rb`:
  Not a real conflict, just upstream getting rid of unused constants too close
  to glitch-soc-specific contents.
  Removed unused constants like upstream did.
- `app/models/trends.rb`:
  Conflict because glitch-soc disabled email notifications for trending links.
  Upstream has refactored this quite a bit and added trending posts.
  Took upstream code, but disabling the extra trending stuff will come in
  another commit.
- `app/views/admin/trends/links/index.html.haml`:
  Conflict due to glitch-soc's theming system.
  Ported upstream changes accordingly.

app/javascript/mastodon/features/compose/components/compose_form.js

@@ -164,8 +164,13 @@ class ComposeForm extends ImmutablePureComponent {
         selectionStart = selectionEnd;
       }
 
-      this.autosuggestTextarea.textarea.setSelectionRange(selectionStart, selectionEnd);
-      this.autosuggestTextarea.textarea.focus();
+      // Because of the wicg-inert polyfill, the activeElement may not be
+      // immediately selectable, we have to wait for observers to run, as
+      // described in https://github.com/WICG/inert#performance-and-gotchas
+      Promise.resolve().then(() => {
+        this.autosuggestTextarea.textarea.setSelectionRange(selectionStart, selectionEnd);
+        this.autosuggestTextarea.textarea.focus();
+      }).catch(console.error);
     } else if(prevProps.isSubmitting && !this.props.isSubmitting) {
       this.autosuggestTextarea.textarea.focus();
     } else if (this.props.spoiler !== prevProps.spoiler) {