Slider: update change event doc

examples/docs/en-US/slider.md

@@ -132,5 +132,5 @@ Set value via a input box.
 ## Events
 | Event Name | Description | Parameters |
 |---------- |-------- |---------- |
-| change | triggers when the value changes | value after changing |
+| change | triggers when the value changes (if the mouse is being dragged, this event only fires when the mouse is released) | value after changing |
 

examples/docs/zh-CN/slider.md

@@ -156,4 +156,4 @@
 ### Events
 | 事件名称      | 说明    | 回调参数      |
 |---------- |-------- |---------- |
-| change | 值改变时触发 | 改变后的值 |
+| change | 值改变时触发（使用鼠标拖曳时，只在松开鼠标后触发） | 改变后的值 |