proposal: bring back the changelog

[MarcoPolo]

I know we've tried this before, but as I do more releases, I'm finding it a bit annoying to have to go through the prior PRs for breaking changes or highlights. Part of this is that I'm not great at updating the issue tracker for the upcoming release, but part of this is that the most context for a change is in the PR that introduces the change.

I'd like to give this another try. Thoughts? @sukunrt

[MarcoPolo]

I thought a bit about how to avoid the pain of needless merge conflicts for the changelog. One strategy is to use a new merge strategy for the changelog.md file. Another strategy is to follow some convention around the commits themselves like Conventional Commits and generate the changelog from that.

Given that Conventional Commits is lighterweight than the changelog, can be verified automatically with a GitHub action, and we have experience with it in js-libp2p. I'm leaning towards trying that first.