docs(index-list): add title slot

Author: dolymood

document/components/docs/en-US/index-list.md

@@ -250,6 +250,7 @@ Each item of `items` array must be an object that must contains the `name` attri
 
 | Name | Description | Scope Parameters |
 | - | - | - |
+| title<sup>1.12.25+</sup> | title slot | - |
 | pulldown<sup>1.9.4+</sup> | located above the list and shown when pulling down refreshing | the detail is the same as Scroll component's pulldown slot scope parameters |
 | pullup<sup>1.9.4+</sup> | located below the list and shown when pulling up loading | the detail is the same as Scroll component's pullup slot scope parameters |
 

document/components/docs/zh-CN/index-list.md

@@ -250,6 +250,7 @@
 
 | 名字 | 说明 | 作用域参数 |
 | - | - | - |
+| title<sup>1.12.25+</sup> | 标题插槽 | - |
 | pulldown<sup>1.9.4+</sup> | 位于列表上方，会在下拉刷新时显示，与 scroll 组件相同 | 具体参考 scroll 组件的 pulldown 插槽作用域参数介绍 |
 | pullup<sup>1.9.4+</sup> | 位于列表下方，会在上拉加载时显示，与 scroll 组件相同  | 具体参考 scroll 组件的 pullup 插槽作用域参数介绍 |