feat: destroy renderables

packages/graphics/container.js

@@ -15,10 +15,17 @@ export class Container extends Renderable {
     this.internal.addChild(child.internal);
   }
 
-  children() {
+  get children() {
     return this._children;
   }
 
+  destroy() {
+    this.children.forEach((child) => {
+      child.destroy();
+    });
+    super.destroy();
+  }
+
   removeChild(child) {
     const index = this._children.indexOf(child);
     if (-1 === index) {

packages/graphics/renderable.js

@@ -8,6 +8,10 @@ export class Renderable {
     this.internal.alpha = alpha;
   }
 
+  destroy() {
+    this.internal.destroy();
+  }
+
   get position() {
     return [this.internal.x, this.internal.y];
   }