[AB-xxx] initial experience leaderboard version

ui/experience-tracking/src/index.tsx

@@ -0,0 +1,19 @@
+import React from 'react';
+import ReactDOM from 'react-dom/client';
+import './index.css';
+import App from './App';
+import {BrowserRouter} from 'react-router-dom';
+import reportWebVitals from './reportWebVitals';
+
+const root = ReactDOM.createRoot(
+  document.getElementById('root') as HTMLElement
+);
+root.render(
+  <React.StrictMode>
+      <BrowserRouter basename={process.env.PUBLIC_URL}>
+        <App />
+      </BrowserRouter>
+  </React.StrictMode>
+);
+
+reportWebVitals();