Update CHANGELOG with the new tooltip feature

Author: gedinakova

CHANGELOG.md

@@ -3,7 +3,13 @@
 All notable changes for each version of this project will be documented in this file.
 
 ## 13.1.0
-
+### New Features
+- `igxTooltipTarget` directive now allows specifying a plain text tooltip without adding an additional DOM element decorated with the `igxTooltip` directive. This is achieved via the newly introduced `tooltip` string input.
+    ```html
+    <button igxTooltipTarget [tooltip]="'Infragistics Inc. HQ'">
+       info
+    </button>
+    ```
 ### General
 
 - `IgxGrid`, `IgxTreeGrid`, `IgxHierarchicalGrid`