Update CHANGELOG.md

Updated getters for the issue #1412

Author: kkarthik11

CHANGELOG.md

@@ -9,6 +9,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Added
 - Added weathersource documentation [#1390](https://github.com/ie3-institute/PowerSystemDataModel/issues/1390)
 - Added standard asset parameter for `3wTransformer` in `ReadTheDocs` [#1417](https://github.com/ie3-institute/PowerSystemDataModel/issues/1417)
+- Added getter sRated for SystemParticipant inputs and updated them in tests in src[#1412](https://github.com/ie3-institute/PowerSystemDataModel/issues/1412)
 
 ### Fixed
 - Fixed small issues in tests [#1400](https://github.com/ie3-institute/PowerSystemDataModel/issues/1400)