feat(dropdown-menu): enable events open and close

src/dropdown-menu/README.en-US.md

@@ -12,6 +12,13 @@ external-classes | Array | - | `['t-class', 't-class-item', 't-class-label', 't-
 show-overlay | Boolean | true | \- | N
 z-index | Number | 11600 | \- | N
 
+### DropdownMenu Events
+
+name | params | description
+-- | -- | --
+open | \- | \-
+close | \- | \-
+
 ### DropdownItem Props
 
 name | type | default | description | required

src/dropdown-menu/README.md

@@ -52,6 +52,13 @@ duration | String / Number | 200 | 动画时长 | N
 show-overlay | Boolean | true | 是否显示遮罩层 | N
 z-index | Number | 11600 | 菜单栏 z-index 层级 | N
 
+### DropdownMenu Events
+
+名称 | 参数 | 描述
+-- | -- | --
+open | \- | 菜单展开时触发
+close | \- | 菜单关闭时触发
+
 ### DropdownMenu 外部样式类
 类名 | 说明
 -- | -- 

src/dropdown-menu/dropdown-menu.ts

@@ -44,6 +44,10 @@ export default class DropdownMenu extends SuperComponent {
         _arrowIcon: calcIcon(v),
       });
     },
+
+    activeIdx(v: number) {
+      this.triggerEvent(v === -1 ? 'close' : 'open');
+    },
   };
 
   methods = {