docs(h-grid): add changelog entry for simpler toolbar template

Author: damyanpetev

CHANGELOG.md

@@ -10,10 +10,22 @@ All notable changes for each version of this project will be documented in this
     - Added new property `toggleNodeOnClick` that determines whether clicking over a node will change its expanded state or not. Set to `false` by default.
 - `IgxPivotGrid`
     - `IPivotDimension` interface now exposes a property called `displayName` similar to the one in the `IPivotValue` interface. This property is optional and will be displayed inside the chips for rows and columns in the `IgxPivotGrid`. If the `displayName` property is not set, `memberName` will be used as a fallback.
+- `IgxHierarchicalGrid`
+    - The declaration of child layout toolbar templates no longer require explicit grid reference so the following:
+        ```html
+        <igx-row-island>
+          <igx-grid-toolbar [grid]="childGrid" *igxGridToolbar="let childGrid">
+        ```
+        can be simplified like:
+        ```html
+        <igx-row-island>
+          <igx-grid-toolbar *igxGridToolbar>
+        ```
 - New directive -  `igxIconButton` directive that provides a way to use an icon as a fully functional button has been added. The new `igxIconButton` comes in three types - flat, outlined and contained (default). All `igxButton`'s with type `icon` will be automatically migrated to the new `igxIconButton`'s with `ng update`.
 - `IgxButton`
     - **Behavioral Change** `buttonSelected` event is now emitted not only when a button gets selected, but also when it gets deselected. However, the event is no longer being emitted on initialization. If this event was used in a scenario where it is assumed that the button gets selected, it's a good idea the logic to be branched now based on `eventArgs.selected` condition.
 
+
 ### General
 - `igxButton`:
     - **Breaking Change** The `raised` type of the `igxButton` directive has been renamed to `contained`. Automatic migrations are available and will be applied on `ng update`.