Update app.js

The file logs the actual port now

Author: Nit-nit

app.js

@@ -70,7 +70,7 @@ const port = 3000;
 app.use(express.static('frontend'));
 
 app.listen(port, () => {
-  console.log('The server is running at http://localhost:3000');
+  console.log('The server is running at http://localhost:'+port);
 });
 `;