Rename all JSX files to have proper file extension

Change-Id: I4ab382f7673a815164f74154e6b03b370fd76a33

src/index.jsx

@@ -0,0 +1,9 @@
+import React from "react";
+import { createRoot } from "react-dom/client";
+import App from "./App";
+
+createRoot(document.getElementById("root")).render(
+  <React.StrictMode>
+    <App />
+  </React.StrictMode>
+);