docs(datepicker): update changelog version, readme prop types

Author: damyanpetev

CHANGELOG.md

@@ -2,6 +2,12 @@
 
 All notable changes for each version of this project will be documented in this file.
 
+## 8.1.2
+
+### New Features
+- `IgxDatePicker`
+    - `valueChange` event is added.
+
 ## 8.1.0
 
 ### New Features
@@ -37,8 +43,6 @@ All notable changes for each version of this project will be documented in this
 - `IgxCombo`
     - Input `[overlaySettings]` - allows an object of type `OverlaySettings` to be passed. These custom overlay settings control how the drop-down list displays.
 - `IgxForOf` now offers usage of local variables `even`, `odd`, `first` and `last` to help with the distinction of the currently iterated element.
-- `IgxDatePicker`
-    - `valueChange` event is added.
 
 
 ## 8.0.2

projects/igniteui-angular/src/lib/date-picker/README.md

@@ -133,12 +133,12 @@ The DatePicker action buttons could be retemplated.
 | Name | Return Type | Description |
 |:--:|:---|:---|
 | `onSelection` | `Date` | Fired when selection is made in the calendar. The event contains the selected value(s) based on the type of selection the component is set to |
-| `onOpened`  | `datePicker` | Emitted when a datePicker calendar is being opened. |
-| `onClosed`  | `datePicker` | An event that is emitted after the calendar is closed. |
-| `onClosing`  | `datePicker` | An event that is emitted when the calendar is being closed |
+| `onOpened`  | `datePicker` | Emitted when a datePicker calendar is opened. |
+| `onClosed`  | `datePicker` | Emitted when a datePicker calendar is closed. |
+| `onClosing`  | `CancelableBrowserEventArgs` | Emitted when a datePicker calendar is being closed. |
 | `onDisabledDate`  | `IDatePickerDisabledDateEventArgs` | Emitted when a disabled date is entered in `dropdown` mode. |
 | `onValidationFailed`  | `IDatePickerValidationFailedEventArgs` | Emitted when an invalid date is entered in `dropdown` mode. |
-| `valueChange` | `IDatePickerValueChangedEventArgs` | Fired when date picker value is changed |
+| `valueChange` | `Date` | Fired when date picker value is changed |
 
 ### Methods
 | Name   | Arguments | Return Type | Description |