Added asset manager.

ts/game/Game.ts

@@ -1,3 +1,4 @@
+import { AssetManager } from "../asset/AssetManager";
 import { Scene } from "../scene/Scene";
 
 type Time = {
@@ -9,9 +10,11 @@ type Time = {
 export class Game {
   public time:Time;
   public scene:Scene|null;
+  public assets:AssetManager;
 
   constructor() {
     this.time = { delta: 0, current: 0, last: 0 };
+    this.assets = new AssetManager();
     this.scene = null;
   }