Adapting changelog for release

Author: sebastian-peter

CHANGELOG.md

@@ -6,6 +6,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased/Snapshot]
 
+## [4.0.0] - 2023-08-01
+
 ### Added
 - Copy methods for container classes [#726](https://github.com/ie3-institute/PowerSystemDataModel/issues/726)
 - Allow hierarchic grid structure for JointGridContainer [#768](https://github.com/ie3-institute/PowerSystemDataModel/issues/768)
@@ -217,7 +219,8 @@ coordinates or multiple exactly equal coordinates possible
 -   CsvDataSource now stops trying to get an operator for empty operator uuid field in entities
 -   CsvDataSource now parsing multiple geoJson strings correctly
 
-[Unreleased/Snapshot]: https://github.com/ie3-institute/powersystemdatamodel/compare/3.0.0...HEAD
+[Unreleased/Snapshot]: https://github.com/ie3-institute/powersystemdatamodel/compare/4.0.0...HEAD
+[4.0.0]: https://github.com/ie3-institute/powersystemdatamodel/compare/3.0.0...4.0.0
 [3.0.0]: https://github.com/ie3-institute/powersystemdatamodel/compare/2.1.0...3.0.0
 [2.1.0]: https://github.com/ie3-institute/powersystemdatamodel/compare/2.0.1...2.1.0
 [2.0.1]: https://github.com/ie3-institute/powersystemdatamodel/compare/2.0.0...2.0.1