updated changelog

Author: chenkasirer

CHANGELOG.md

@@ -10,6 +10,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Added
 
 * Added support for `Mkdocs` documentation generation, using `mkdocs.docs` task. (`Mkdocs` is an optional dependency at the moment, but may become a required dependency in the future).
+* Added support for pruning old documentation versions with `mkdocs.prune` task.
 
 ### Changed