Add docs about hiddenColumns property of <DataTable>.

Author: Madeorsk

docs/DataTable.md

@@ -836,6 +836,25 @@ export const ReviewList = () => (
 );
 ```
 
+## `hiddenColumns`
+
+By default, `<DataTable>` renders all `<DataTable.Col>` children. Use the `hiddenColumns` property to set hidden columns by default.
+
+Using the `hiddenColumns` property instead of removing `<DataTable.Col>` elements entirely allows hidden columns to be displayed again using a `ColumnsButton`, as in [Hiding or Reordering](#hiding-or-reordering-columns) section.
+
+```tsx
+const PostList = () => (
+    <List actions={<PostListActions />}>
+        <DataTable hiddenColumns={['id', 'author']}>
+            <DataTable.Col source="id" />
+            <DataTable.Col source="title" />
+            <DataTable.Col source="author" />
+            <DataTable.Col source="year" />
+        </DataTable>
+    </List>
+);
+```
+
 ## `size`
 
 The `<DataTable>` is designed for a high content density, so the row padding is low. If you want to add more margin to each cell, set the `size` prop to `medium`.