[doc] add more entries to dropdown doc API

components/dropdown/index.en-US.md

@@ -19,6 +19,8 @@ If there are too many operations to display, you can wrap them in a `Dropdown`.
 | disabled | whether the dropdown menu is disabled | boolean | - |
 | getPopupContainer | to set the container of the dropdown menu. The default is to create a `div` element in `body`, you can reset it to the scrolling area and make a relative reposition. [example](https://codepen.io/afc163/pen/zEjNOy?editors=0010) | Function(triggerNode) | `() => document.body` |
 | overlay | the dropdown menu | [Menu](/components/menu) | - |
+| overlayClassName | Class name of the dropdown root element | string | - |
+| overlayStyle | Style of the dropdown root element | object | - |
 | placement | placement of pop menu: `bottomLeft` `bottomCenter` `bottomRight` `topLeft` `topCenter` `topRight` | String | `bottomLeft` |
 | trigger | the trigger mode which executes the drop-down action | Array<`click`\|`hover`\|`contextMenu`> | `['hover']` |
 | visible | whether the dropdown menu is visible | boolean | - |

components/dropdown/index.zh-CN.md

@@ -20,6 +20,8 @@ title: Dropdown
 | disabled | 菜单是否禁用 | boolean | - |
 | getPopupContainer | 菜单渲染父节点。默认渲染到 body 上，如果你遇到菜单滚动定位问题，试试修改为滚动的区域，并相对其定位。[示例](https://codepen.io/afc163/pen/zEjNOy?editors=0010) | Function(triggerNode) | `() => document.body` |
 | overlay | 菜单 | [Menu](/components/menu) | - |
+| overlayClassName | 下拉根元素的类名称 | string | - |
+| overlayStyle | 下拉根元素的样式 | object | - |
 | placement | 菜单弹出位置：`bottomLeft` `bottomCenter` `bottomRight` `topLeft` `topCenter` `topRight` | String | `bottomLeft` |
 | trigger | 触发下拉的行为 | Array<`click`\|`hover`\|`contextMenu`> | `['hover']` |
 | visible | 菜单是否显示 | boolean | - |