Remove unused javascript (#2470)

src/app/pages/App.tsx

@@ -1,4 +1,4 @@
-import React from 'react';
+import React, { useEffect } from 'react';
 import { Provider as JotaiProvider } from 'jotai';
 import { RouterProvider } from 'react-router-dom';
 import { QueryClient, QueryClientProvider } from '@tanstack/react-query';
@@ -13,9 +13,19 @@ import { ScreenSizeProvider, useScreenSize } from '../hooks/useScreenSize';
 
 const queryClient = new QueryClient();
 
+const useLastNodeToDetectReactPortalEntry = () => {
+  useEffect(() => {
+    const lastDiv = document.createElement('div');
+    lastDiv.setAttribute('data-last-node', 'true');
+    document.body.appendChild(lastDiv);
+  }, []);
+};
+
 function App() {
   const screenSize = useScreenSize();
 
+  useLastNodeToDetectReactPortalEntry();
+
   return (
     <ScreenSizeProvider value={screenSize}>
       <FeatureCheck>