fixed favicons and added service-worker

Signed-off-by: Pascal Syma <pascal@syma.dev>

src/index.js

@@ -37,4 +37,10 @@ const config = {
     }
 };
 
+if ('serviceWorker' in navigator) {
+    window.addEventListener('load', () => {
+        navigator.serviceWorker.register('./service-worker.js').then();
+    });
+}
+
 const game = new Phaser.Game(config);