Generate changelog between last release and current nightly

[wlhlm]

Generate changelog between last release and current nightly. I think that's a bit more informative than the changelog from one nightly version to the previous nightly as those usually only include a handful of changes at most.

Drawback is that if there's a new release, the nightly-non-nightly changelog for the old release will stick around (and stop getting updated) and eventually need manual cleanup. That won't happen that often and should be manageable.

Fixes a bug with the --previous-release-name parameter of gtnh.cli.generate_changelog which made it not work at all.

[Alexdoru]

The changelog from nightly to nightly is very useful to track down bugs that appear in between versions and that are caused by cross mod interactions (so you can't just open one project and look at the git history of that one project). Please don't delete the nightly to nightly changelog, you can add the last stable to current nightly changelog as a separate second file.

[wlhlm]

Uhh, I haven't touched the nightly-nightly changelogs. This just adds another type.

[Alexdoru]

Good