Merge pull request #5070 from IgniteUI/SAndreeva/update-changelog-8.0.0

Update CHANGELOG.md with pickers new functionality

Author: kdinev

CHANGELOG.md

@@ -14,7 +14,11 @@ All notable changes for each version of this project will be documented in this
     - `openDialog()` now has an optional `[target: HTMLElement]` parameter. It's used in `mode="dropdown"` and the drop down container is positioned according to the provided target.
     - The custom drop down template target is no longer marked with `#dropDownTarget`, instead it's provided as an `HTMLElement` to the `openDialog()` method.
     - By default, the `igxDatePicker` drop down target is changed from the `igxInput` element to the `igxInputGroup` element.
-
+    - `onClosing` event is added.
+    - **Breaking Change** `onOpen` event is renamed to `onOpened`.
+    - **Breaking Change** `onClose` event is renamed to `onClosed`.
+    - **Behavioral Change** - action buttons are now available in the dropdown mode.
+    - **Feature** `igxDatePicker` and `igxTimePicker` now provide the ability for adding custom action buttons. Read up more information in [igxDatePicker ReadMe](https://github.com/IgniteUI/igniteui-angular/tree/master/projects/igniteui-angular/src/lib/date-picker/README.md) or [igxTimePicker ReadMe](https://github.com/IgniteUI/igniteui-angular/tree/master/projects/igniteui-angular/src/lib/time-picker/README.md)
 
 ## 7.3.4