[Glitch] Rewrite actions/app.ts and reducers/missed_updates.ts with createAction

Port 0999cb4601 to glitch-soc

Signed-off-by: Claire <claire.github-309c@sitedethib.com>

app/javascript/flavours/glitch/actions/app.ts

@@ -0,0 +1,7 @@
+import { createAction } from '@reduxjs/toolkit';
+
+type ChangeLayoutPayload = {
+  layout: 'mobile' | 'single-column' | 'multi-column';
+};
+export const changeLayout =
+  createAction<ChangeLayoutPayload>('APP_LAYOUT_CHANGE');