docs: update menu doc

Author: tangjinzhou

components/menu/index.en-US.md

@@ -52,11 +52,12 @@
 
 | Param | Description | Type | Default value |
 | ----- | ----------- | ---- | ------------- |
-| children | sub menus or sub menu items | Array<MenuItem\|SubMenu> |  |
 | disabled | whether sub menu is disabled or not | boolean | false |
 | key | unique id of the sub menu | string |  |
 | title | title of the sub menu | string\|slot |  |
 
+The children of Menu.SubMenu must be `MenuItem` or `SubMenu`.
+
 ### Menu.SubMenu Events
 | Events Name | Description | Arguments |
 | --- | --- | --- |
@@ -69,6 +70,8 @@
 | children | sub menu items | MenuItem\[] |  |
 | title | title of the group | string\|slot |  |
 
+The children of Menu.ItemGroup must be `MenuItem`.
+
 ### Menu.Divider
 
 Divider line in between menu items, only used in vertical popup Menu or Dropdown Menu.

components/menu/index.zh-CN.md

@@ -50,13 +50,15 @@
 
 | 参数 | 说明 | 类型 | 默认值 |
 | --- | --- | --- | --- |
-| children | 子菜单的菜单项 | Array<MenuItem\|SubMenu> |  |
 | disabled | 是否禁用 | boolean | false |
 | key | 唯一标志 | string |  |
 | title | 子菜单项值 | string\|slot |  |
 
+Menu.SubMenu 的子元素必须是 `MenuItem` 或者 `SubMenu`.
+
 ### SubMenu事件
 | 事件名称 | 说明 | 回调参数 |
+| --- | --- | --- |
 | titleClick | 点击子菜单标题 | ({ key, domEvent }) |
 
 ### Menu.ItemGroup
@@ -65,6 +67,8 @@
 | --- | --- | --- | --- |
 | title | 分组标题 | string\|\|function\|slot |  |
 
+Menu.ItemGroup 的子元素必须是 `MenuItem`.
+
 ### Menu.Divider
 
 菜单项分割线，只用在弹出菜单内。

scripts/gulpfile.js

@@ -60,10 +60,7 @@ function copyHtml() {
     path.join(cwd, 'site-dist/index-cn.html'),
     fs.readFileSync(path.join(cwd, 'site-dist/index.html')),
   );
-  fs.writeFileSync(
-    path.join(cwd, 'site-dist/CNAME'),
-    'vue.ant.design',
-  );
+  fs.writeFileSync(path.join(cwd, 'site-dist/CNAME'), 'vue.ant.design');
   rl.on('line', line => {
     if (line.indexOf('path:') > -1) {
       const name = line.split("'")[1].split("'")[0];

types/menu/sub-menu.d.ts

@@ -19,12 +19,6 @@ export declare class SubMenu extends AntdComponent {
    */
   disabled: boolean;
 
-  /**
-   * sub menus or sub menu items
-   * @type Array<MenuItem | SubMenu>
-   */
-  children: Array<MenuItem | SubMenu>;
-
   /**
    * title of the sub menu
    * @type string | slot