Update CHANGELOG

Signed-off-by: Marijn van Wezel <96489967+marijnvanwezel@users.noreply.github.com>

Author: marijnvanwezel

CHANGELOG.md

@@ -6,7 +6,14 @@ file. A changelog has been kept from version 5.0.0 onwards.
 The format is based on [Keep a Changelog], and this project adheres to
 [Semantic Versioning].
 
-## 5.0.0 - 2022-01-09
+## 6.0.0 - 2023-09-19
+
+### Changed
+
+- Change the license from the GPL-v2.0-or-later license to the more permissive
+  MIT license.
+
+## 5.0.0 - 2023-01-09
 
 ### Added