Fixes room list, adds OpenGraph so link previews look good

server.js

@@ -352,6 +352,14 @@ app.get('/', (req, res) => {
   res.sendFile(path.join(__dirname, 'public', 'menu.html'));
 });
 
+app.get('/api/rooms', (req, res) => {
+  const roomList = Object.keys(games).map(name => ({
+    name,
+    playerCount: games[name].players.length
+  }));
+  res.json({ rooms: roomList });
+});
+
 // Socket.IO connection handling
 io.on('connection', (socket) => {
   let currentRoom = null;