update docs

packages/artplayer/src/layers.js

@@ -13,13 +13,20 @@ export default class Layers {
 
   add(item, callback) {
     if (!item.disable) {
-      const { refs: { $layers } } = this.art;
+      const { refs: { $layers }, events: { proxy } } = this.art;
       id++;
       const $layer = document.createElement('div');
       $layer.setAttribute('class', `art-layer art-layer-${item.name || id}`);
       setStyle($layer, 'z-index', item.index || id);
       append($layer, item.html);
       setStyles($layer, item.style || {});
+      if (item.click) {
+        proxy($layer, 'click', event => {
+          event.preventDefault();
+          item.click.call(this, event);
+          this.art.emit('layers:click', $layer);
+        });
+      }
       this.art.emit('layers:add', $layer);
       callback && callback($layer);
       insertByIndex($layers, $layer, item.index || id);