chore(*): update changelog with header navigation

Author: ddincheva

CHANGELOG.md

@@ -64,6 +64,17 @@ All notable changes for each version of this project will be documented in this
     - `deselectColumns` API method is added for the `IgxGrid`. It allows to deselect columns by passing array of IgxColumnComponent or column fields.
     - `deselectAllColumns` API method is added for the `IgxGrid`. It allows to deselect all columns.
     - `getSelectedColumnsData` API method is added for the `IgxGrid`. It allows to get the selected columns data.
+    KeyBoard navigation support in the IgxGrid headers. Now is possible to navigate with the arrows keys through grid headers. Also we provide a number of key combinations that trigger a different column functionality like filtering, sorting, grouping and etc. You can read more information in the [Grid Specification](https://github.com/IgniteUI/igniteui-angular/wiki/igxGrid-Specification#kb-navigation).
+    - **Behavioral Change**
+        - *you can not use* `tab` key to navigate between the cell in the Igx Grid. The navigation is performed only with arrow keys.
+        - when you are in edit mode with `tab` key you can navigate to the next editable cell.
+        - The grid introduces the following basic `tab stops`:
+            - Toolbar / Group by Area if existing;
+            - The first cell in the header row;
+            - The first cell in the first body row;
+            - The first cell in column summary if exists;
+            - Pager UI;
+    - `onGridKeydown` event is deprecated. Now you can directly bind to keydown on the IgxGrid component in order to perform custom keyboard navigation.
 
 - `IgxCombo`:
     - Added `autoFocusSearch` input that allows to manipulate the combo's opening behavior. When the property is `true` (by default), the combo's search input is focused on open. When set to `false`, the focus goes to the combo items container, which can be used to prevent the software keyboard from activating on mobile devices when opening the combo.