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

Conflicts:
- `.github/ISSUE_TEMPLATE/bug_report.md`:
  Upstream added the `bug` label to bug reports.
  Did the same.
- `app/services/fan_out_on_write_service.rb`:
  Upstream put DMs back into timelines, glitch-soc was already doing it.
  Ignored upstream changes.

app/javascript/mastodon/actions/app.js

@@ -8,3 +8,10 @@ export const focusApp = () => ({
 export const unfocusApp = () => ({
   type: APP_UNFOCUS,
 });
+
+export const APP_LAYOUT_CHANGE = 'APP_LAYOUT_CHANGE';
+
+export const changeLayout = layout => ({
+  type: APP_LAYOUT_CHANGE,
+  layout,
+});