Support to check the validation against a PR

[LinuxSuRen]

Let assume, you put all Releaser resource files into a git repository, and manage it via Argo CD. In this case, it's great to do the resource spec validation against a Pull request.

What to do

• Provide a webhook endpoint to receive the SCM events from a git provider (such as Github, Gitlab, etc.)
• Add a comment to a PR to show the validation result