Add the ability to add a header to the top of the comments

[ben-of-codecraft]

Feature

Would love a way to apply a header to the top of the comment when sent to the PR. We do this internally so it shows the current version of the action was run, the latest version available and instructions inline on what commands can be taken in comments.

I can submit a PR on how we do it, but it's got some jank in how it does it.

Please notify me if you want me to submit a PR on this.

[smasodeans]