To remove the opportunity for junk to enter into the changelog, and to reduce the commit history, the changlog generation will only happen on release, and only based on merged PRs. Fixes #205
https://github.blog/changelog/2020-10-01-github-actions-deprecating-set-env-and-add-path-commands
Thanks: https://renehernandez.io/essays/2020/09/23/automate-changelog-and-releases-creation-in-github