DataGrid: Add shortcuts to Row Selection demo (#30126)

Author: arman-boyakhchyan

apps/demos/Demos/DataGrid/MultipleRecordSelectionModes/description.md

@@ -5,4 +5,10 @@ To configure when the checkboxes appear, set the [showCheckBoxesMode](/Documenta
 The checkbox in the header selects all rows or current page rows, depending on the [selectAllMode](/Documentation/ApiReference/UI_Components/dxDataGrid/Configuration/selection/#selectAllMode) value. If you want to disable this checkbox, set [allowSelectAll](/Documentation/ApiReference/UI_Components/dxDataGrid/Configuration/selection/#allowSelectAll) to **false**.
 
 In this demo, you can use the drop-down menus under the grid to change the **showCheckBoxesMode** and **selectAllMode** values.
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+If **showCheckBoxesMode** is *"always"*, you can select and unselect a row by clicking its checkbox. Focus the component's data cells with the arrow keys, **Tab**, **Shift+Tab**, **Home**, and **End**, and press **Space** to select or unselect a row.
+
+If **showCheckBoxesMode** is *"none"*, *"onCLick"*, or *"onLongTap"*, you can click a row or focus a data cell and press **Space** to select a row. Unselect a row or select one without clearing previous selection with **Ctrl+Click**/**Ctrl+Space**.
+
+Use **Shift+Click**/**Shift+Space** to select all items between two rows. For more details, refer to the DataGrid [Keyboard Navigation](/Documentation/Guide/UI_Components/DataGrid/Accessibility/#Keyboard_Navigation) help topic.

apps/demos/Demos/DataGrid/RowSelection/description.md

@@ -1,4 +1,4 @@
-In this demo, the DataGrid allows users to select only one row at a time. To enable this mode, set the **selection**.[mode](/Documentation/ApiReference/UI_Components/dxDataGrid/Configuration/selection/#mode) property to *"single"*. Press Ctrl to unselect a row.
+In this demo, the DataGrid allows users to select only one row at a time. To enable this mode, set the **selection**.[mode](/Documentation/ApiReference/UI_Components/dxDataGrid/Configuration/selection/#mode) property to *"single"*. You can click a row to select it, and **Ctrl+Click** to unselect it. Focus the component's data cells with the arrow keys, **Tab**, **Shift+Tab**, **Home**, and **End**, and press **Space** to select a row. Use **Ctrl+Space** to unselect the selected row.
 
 You can access the selected row data from the [onSelectionChanged](/Documentation/ApiReference/UI_Components/dxDataGrid/Configuration/#onSelectionChanged) function. In this demo, this function fetches the selected row's information and displays it under the grid.
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