Fix pop-out player appearing on mobile screens in web UI (#15157)

Fix #15092

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,
+});