Mechanism to keep a better Changelog

[crisptrutski]

It would be nice if it automatically summarize the PRs.

As far as breaking API changes (especially subtle semantics), I'm not sure how best to make sure we don't forget those.

[crisptrutski]

Idea: just validate in CI that there is a line item in our CHANGELOG for the version

[piranha]

another idea: release is a separate manual CI action