please add openVALIDATION Project to readme (OpenAPITools#5534)

* added openVALIDATION Project to readme

* Update README.md

Co-Authored-By: Akihito Nakano <[email protected]>

Co-authored-by: Akihito Nakano <[email protected]>

Author: 2 people

README.md

@@ -615,6 +615,7 @@ Here are some companies/projects (alphabetical order) using OpenAPI Generator in
 - [Myworkout](https://myworkout.com)
 - [NamSor](https://www.namsor.com/)
 - [Openet](https://www.openet.com/)
+- [openVALIDATION](https://openvalidation.io/)
 - [Oracle](https://www.oracle.com/)
 - [Paxos](https://www.paxos.com)
 - [Ponicode](https://ponicode.dev/)