Add a Github Action for config file validation

[kehoecj]

The config-file-validator is a good candidate for a Github Action so users can easily integration configuration validation into their existing Github Action workflows. There is a working proof of concept that can pretty much be directly migrated over to this project.

[ghanem-mhd]

I'm interested in contributing. Before proceeding, I'd like to confirm that the intended change is to migrate the GitHub Action code to be integrated within the config-file-validator repository.

However, I came across a recommendation in the GitHub documentation suggesting that if the action is intended for public use, it's best to maintain it in a separate repository. Here's the link for reference: Choosing a location for your action - GitHub Docs. WDTY?