Set up proper changelog and release notes

[Rosey]

When I started on this project I was just kind of doing it for myself but I think it has enough people using it that I should be a bit more diligent (and probably should have been from the start, let's be honest) about explaining what changed in each version.

[Rosey]

I set up a super basic changelog.md file but it could definitely be improved upon. I kind of hate my release workflow right now, nothing is automated and it feels like I really ought to take advantage of some automation here.