Fixed the index.js

client/src/index.js

@@ -1,10 +1,11 @@
 import React from 'react';
-import ReactDOM from 'react-dom';
+import ReactDOM from "react-dom/client";
 import App from './App';
 
-ReactDOM.render(
+const root = ReactDOM.createRoot(document.getElementById('root'));
+
+root.render(
   <React.StrictMode>
     <App />
-  </React.StrictMode>,
-  document.getElementById('root')
+  </React.StrictMode>
 );