Implemented secure WebSocket connection based on the current protocol.

public/app.js

@@ -1,4 +1,5 @@
-const socket = new WebSocket(`ws://${window.location.host}`);
+const protocol = window.location.protocol === 'https:' ? 'wss:' : 'ws:';
+const socket = new WebSocket(`${protocol}//${window.location.host}`);
 
 socket.addEventListener('open', () => {
   console.log('WebSocket connection established');