Shut down A-Frame and three.js on exit

src/room.js

@@ -119,6 +119,10 @@ async function exitScene() {
   if (NAF.connection && NAF.connection.adapter) {
     NAF.connection.disconnect();
   }
+
+  const scene = document.querySelector("a-scene");
+  scene.renderer.animate(null); // Stop animation loop, TODO A-Frame should do this
+  document.body.removeChild(scene);
 }
 
 async function enterScene(mediaStream) {