Add GitHub Codeowners Validator action

Action that ensures the correctness of your GitHub CODEOWNERS file. Link to the GitHub repository: https://github.com/mszostok/codeowners-validator

Author: mszostok

README.md

@@ -143,6 +143,7 @@ Set up your GitHub Actions workflow with a specific version of your programming
 - [Prow GitHub Actions](https://github.com/jpmcb/prow-github-actions) - Automation of policy enforcement, chat-ops, and automatic PR merging.
 - [Check GitHub Status in your Workflow](https://github.com/crazy-max/ghaction-github-status)
 - [Manage Labels on GitHub (create/rename/update/delete) as Code](https://github.com/crazy-max/ghaction-github-labeler)
+- [GitHub Codeowners Validator](https://github.com/mszostok/codeowners-validator) - Ensures the correctness of your GitHub CODEOWNERS file. It supports public and private GitHub repositories and also GitHub Enterprise installations.
 
 ### Collection of Actions