changelog: Add changelog entry

Author: jorisv

CHANGELOG.md

@@ -6,6 +6,9 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 
 ## [Unreleased]
 
+### Fixed
+- Fix unit test build in C++11 ([#442](https://github.com/stack-of-tasks/eigenpy/pull/442))
+
 ## [3.4.0] - 2024-02-26
 
 ### Added