replace react-js with react-ts

frontend/src/App.tsx

@@ -22,7 +22,7 @@ function App() {
           count is {count}
         </button>
         <p>
-          Edit <code>src/App.jsx</code> and save to test HMR
+          Edit <code>src/App.tsx</code> and save to test HMR
         </p>
       </div>
       <p className="read-the-docs">

frontend/src/main.tsx

@@ -1,9 +1,9 @@
 import { StrictMode } from 'react'
 import { createRoot } from 'react-dom/client'
 import './index.css'
-import App from './App.jsx'
+import App from './App.tsx'
 
-createRoot(document.getElementById('root')).render(
+createRoot(document.getElementById('root')!).render(
   <StrictMode>
     <App />
   </StrictMode>,

frontend/src/vite-env.d.ts

@@ -0,0 +1 @@
+/// <reference types="vite/client" />