[changelog skip] Ensure PRs include a Changelog entry
[changelog skip] Ensure PRs include a Changelog entry

The goal of this PR is to add a github action that checks for the presence of a changelog entry.

It is better to add entries as a PR is merged instead of having to remember what was merged and generate a changelog at release time.

By automating this check, it's one less thing the maintainer has to remember, and it's one less thing a change might be blocked on i.e. "Looks good, but please add a changelog entry".

Let me know if you have any questions and Happy Friday!

heroku/heroku-buildpack-clojure,heroku/heroku-buildpack-clojure