Add stricter ESLint rules for Typescript files (#24926)

app/javascript/mastodon/actions/app.ts

@@ -1,11 +1,12 @@
 import { createAction } from '@reduxjs/toolkit';
+
 import type { LayoutType } from '../is_mobile';
 
 export const focusApp = createAction('APP_FOCUS');
 export const unfocusApp = createAction('APP_UNFOCUS');
 
-type ChangeLayoutPayload = {
+interface ChangeLayoutPayload {
   layout: LayoutType;
-};
+}
 export const changeLayout =
   createAction<ChangeLayoutPayload>('APP_LAYOUT_CHANGE');