Update CHANGELOG.md

Author: GrahamCampbell

CHANGELOG.md

@@ -12,6 +12,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 * Add support for the confidential filter in `Issues:all()`
 * Allow specifying params in `Wiki::showAll()`
 * Allow specifying params in `SystemHooks::create()`
+* Allow `chmod` action and `execute_filemode` attribute
 * Implement group merge requests endpoints
 * Implement event endpoints