add link to .NET version

Author: hf-kklein

README.md

@@ -10,6 +10,8 @@
 
 This package provides mostly autogenerated [pydantic](https://docs.pydantic.dev/latest/)-based model classes for the MaLo ident API.
 
+We also maintain a [C#/.NET Version of this data model](https://github.com/Hochfrequenz/malo-ident-net-models).
+
 It does not provide you with an HTTP client.
 
 ## Installation