Fix import path of reportWebVitals

Author: eomielan

frontend/src/index.js

@@ -2,7 +2,7 @@ import React from "react";
 import ReactDOM from "react-dom/client";
 import "./index.css";
 import App from "./App.js";
-import reportWebVitals from "./reportWebVitals";
+import reportWebVitals from "./reportWebVitals.js";
 
 const root = ReactDOM.createRoot(document.getElementById("root"));
 root.render(