Add changelog entry for macos github action

Author: ianfixes

CHANGELOG.md

@@ -12,6 +12,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 - Code coverage tooling
 - Explicit check and warning for library directory names that do not match our guess of what the library should/would be called
 - Symlink tests for `Host`
+- GitHub action for MacOS
 
 ### Changed
 - Arduino backend is now `arduino-cli` version `0.13.0`