prepare minor release

Author: nyamsprod

CHANGELOG.md

@@ -2,7 +2,7 @@
 
 All Notable changes to `Csv` will be documented in this file
 
-## [Next](https://github.com/thephpleague/csv/compare/9.20.1...master) - TBD
+## [9.21.0](https://github.com/thephpleague/csv/compare/9.20.1...9.21.0) - 2025-01-08
 
 ### Added