Update CHANGELOG for 2.13.0-beta2

Author: AndrewDavidoff

CHANGELOG.md

@@ -9,6 +9,12 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 ### Deprecated
 - Deprecated Office2013.Word.Person.Contact property. It no longer persists and will be removed in a future version (#912)
 
+Release Notes:
+## Version 2.13.0-beta2 - 2021-04-20
+
+### Added
+- Additional O19 types to match Open Specifications (#916)
+
 ## Version 2.13.0-beta1 - 2021-03-09
 
 ### Added