[Improvement] Popup: add click-overlay event (#647)

docs/markdown/en-US/popup.md

@@ -49,3 +49,9 @@ Use `position` prop to set popup display position
 | transition | Transition | `String` | `popup-slide` | - |
 | prevent-scroll | Prevent background scroll | `Boolean` | `false` | - |
 | get-container | Return the mount node for Popup | `Function` | - | `() => HTMLElement` |
+
+### Event
+
+| Event | Description | Arguments |
+|-----------|-----------|-----------|
+| click-overlay | Triggered when click overlay | - |