please add openVALIDATION Project to readme

Created by: thecodemonkey

please add openVALIDATION Project to the readme.

This open source project includes the integration of openVALIDATION into OpenAPI. It enables the specification of complex validation rules within a service contract using natural language. Thus, both the service stubs and the client proxies including validation logic can be generated automatically. read more...

validation rules can also be generated separately.

sample:

openapi: "3.0.0"
info:
  version: 1.0.0
  title: sample
paths:
  /:
    post:
      requestBody:
        content:
          application/json:
            schema:
              properties:
                name:
                  type: string
                mail:
                  type: number
            x-ov-rules:
              culture: en
              rule: |  
                the name of applicant has to be Alex
                and his mail must not be alex@yahoo.com
      responses:
        '200':
          description: ok

PR checklist

• [ x ] Read the contribution guidelines.
• [ x ] If contributing template-only or documentation-only changes which will change sample output, build the project before.