Prepare 25.4.0

Author: hynek

CHANGELOG.md

@@ -13,7 +13,7 @@ You can find our backwards-compatibility policy [here](https://github.com/hynek/
 <!-- changelog follows -->
 
 
-## [Unreleased](https://github.com/hynek/structlog/compare/25.3.0...HEAD)
+## [25.4.0](https://github.com/hynek/structlog/compare/25.3.0...25.4.0) - 2025-06-02
 
 ### Added