Fix forEach function

packages/artplayer/src/layer.js

@@ -6,9 +6,7 @@ export default class Layer extends Component {
         this.name = 'layer';
         this.$parent = art.template.$layer;
         art.once('ready', () => {
-            art.option.layers.forEach(item => {
-                this.add(item);
-            });
+            art.option.layers.forEach((item) => this.add(item));
         });
     }
 }