Now that we're stable and starting to ship packages via brew (#11), Alpine (#alpinelinux/aports/pull/3182), and RPM (#111), we may want to move the changelog out of the README into a CHANGELOG.md file, and find a way to include it in various packages, git version tags, etc. (Per the discussion in #111 in particular.)

The extent to which we can auto-generate such logs in the first place, the better, but this issue is focused on taking the already-written CHANGELOG.md contents and reusing them elsewhere.

A potential source of inspiration: https://keepachangelog.com/en/1.0.0/