Update CHANGELOG

Author: Rahix

CHANGELOG.md

@@ -5,6 +5,10 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 ## [Unreleased]
+### Added
+- Support for `ATmega4808` ([#137]).
+
+[#137]: https://github.com/Rahix/avr-device/pull/137
 
 
 ## [0.5.2] - 2023-08-24