add: boilerplate w/ navbar, tailwindcss

frontend/src/main.jsx

@@ -1,10 +1,8 @@
-import React from 'react'
 import ReactDOM from 'react-dom/client'
-import App from './App.jsx'
+import { RouterProvider } from 'react-router-dom'
+import router from './router'
 import './index.css'
 
 ReactDOM.createRoot(document.getElementById('root')).render(
-  <React.StrictMode>
-    <App />
-  </React.StrictMode>,
-)
+    <RouterProvider router={router} />
+)