changelog for 2.4.8 (#12950)

* changelog for 2.4.8

* Update CHANGELOG.en-US.md

* Update CHANGELOG.es.md

CHANGELOG.en-US.md

 ## Changelog
 
+### 2.4.8
+
+- Not displaying outline when Switch is focused, #12771
+- Fixed Dropdown's style in ButtonGroup, #12819 (by @bluejfox)
+- Added opened event for Dialog, #12828
+- Fixed the incorrect display order of TabNav, #12846
+- Fixed the problem that Tabs did not scroll to the selected tab, #12948
+- Fixed the problem that the identifier does not display when the Tree node is dragged, #12854
+- The validate event parameter of Form contains the validation message, #12860 (by @YamenSharaf)
+- Fixed DatePicker not to verify the validity of user input time, #12898
+- Fixed the problem that `render-header` attribute of Table header doesn't work, #12914
+
 ### 2.4.7
 
 *2018-09-14*

CHANGELOG.es.md

 ## Changelog
 
+### 2.4.8
+
+- Not displaying outline when Switch is focused, #12771
+- Fixed Dropdown's style in ButtonGroup, #12819 (by @bluejfox)
+- Added opened event for Dialog, #12828
+- Fixed the incorrect display order of TabNav, #12846
+- Fixed the problem that Tabs did not scroll to the selected tab, #12948
+- Fixed the problem that the identifier does not display when the Tree node is dragged, #12854
+- The validate event parameter of Form contains the validation message, #12860 (by @YamenSharaf)
+- Fixed DatePicker not to verify the validity of user input time, #12898
+- Fixed the problem that `render-header` attribute of Table header doesn't work, #12914
+
 ### 2.4.7
 
 *2018-09-14*

CHANGELOG.zh-CN.md

 ## 更新日志
 
+### 2.4.8
+
+- Switch 聚焦时不显示轮廓，#12771
+- 修复 Dropdown 在 ButtonGroup 中样式问题，#12819 （by @bluejfox）
+- Dialog 新增 opened 事件，#12828
+- 修复 TabNav 显示顺序不正确的问题，#12846
+- 修复 Tabs 没有滑动到选中 tab 的问题，#12948
+- 修复 Tree 节点在拖拽时标识符不显示的问题，#12854
+- Form 的 validate 事件参数中包含了校验的信息，#12860 （by @YamenSharaf）
+- 修复 DatePicker 没有校验用户输入时间的合法性问题，#12898
+- 修复 Table 表头的 `render-header`属性不生效的问题，#12914
+
 ### 2.4.7
 
 *2018-09-14*