updated changelog

Author: clausnagel

CHANGELOG.md

@@ -98,7 +98,8 @@
 The changelog of previous citygml-tools releases before version 2.0 is available
 [here](https://github.com/citygml4j/citygml-tools/blob/citygml-tools-v1/CHANGES.md).
 
-[Unreleased]: https://github.com/citygml4j/citygml-tools/compare/v2.2.0..HEAD
+[Unreleased]: https://github.com/citygml4j/citygml-tools/compare/v2.3.0..HEAD
+[2.3.0]: https://github.com/citygml4j/citygml-tools/releases/tag/v2.3.0
 [2.2.0]: https://github.com/citygml4j/citygml-tools/releases/tag/v2.2.0
 [2.1.0]: https://github.com/citygml4j/citygml-tools/releases/tag/v2.1.0
 [2.0.0]: https://github.com/citygml4j/citygml-tools/releases/tag/v2.0.0