Update CHANGELOG.md

Author: GrahamCampbell

CHANGELOG.md

@@ -7,6 +7,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [10.2.0] - UPCOMING
 
+* Added variable_type to addVariable and updateVariable
+
 [10.2.0]: https://github.com/GitLabPHP/Client/compare/10.1.1...10.2.0
 
 ## [10.1.1] - 2020-10-26