Add the index controller

src/Controller/ConferenceController.php

@@ -0,0 +1,23 @@
+<?php
+
+namespace App\Controller;
+
+use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
+use Symfony\Component\HttpFoundation\Response;
+use Symfony\Component\Routing\Attribute\Route;
+
+class ConferenceController extends AbstractController
+{
+    #[Route('/', name: 'homepage')]
+    public function index(): Response
+    {
+        return new Response(<<<EOF
+            <html>
+                <body>
+                    <img src="/images/under-construction.gif" />
+                </body>
+            </html>
+            EOF
+        );
+    }
+}