feat(tbale): 分组表头支持固定-1.x (#3896)

* feat(table): 分组表头支持固定

* docs(table): 增加分组表头固定的英文文档

antdv-demo/docs/table/index.en-US.md

@@ -111,6 +111,7 @@ One of the Table `columns` prop for describing the table's columns, Column has t
 | Property | Description | Type | Default |
 | --- | --- | --- | --- |
 | title | Title of the column group | string\|slot | - |
+| fixed | Set column group to be fixed: `true`(same as left) `'left'` `'right'` | boolean\|string | `false` |  |
 | slots | When using columns, you can use this property to configure the properties that support the slot, such as `slots: { title: 'XXX'}` | object | - |
 
 ### pagination

antdv-demo/docs/table/index.zh-CN.md

@@ -111,6 +111,7 @@
 | 参数 | 说明 | 类型 | 默认值 |
 | --- | --- | --- | --- |
 | title | 列头显示文字 | string\|slot | - |
+| fixed | 列是否固定，可选 `true`(等效于 left) `'left'` `'right'` | boolean\|string | false |  |
 | slots | 使用 columns 时，可以通过该属性配置支持 slot 的属性，如 `slots: { title: 'XXX'}` | object | - |
 
 ### pagination

components/table/ColumnGroup.jsx

@@ -3,6 +3,7 @@ import PropTypes from '../_util/vue-types';
 export default {
   name: 'ATableColumnGroup',
   props: {
+    fixed: PropTypes.oneOfType([PropTypes.bool, PropTypes.oneOf(['left', 'right'])]),
     title: PropTypes.any,
   },
   __ANT_TABLE_COLUMN_GROUP: true,