Neat 0.7.0: Tentative Windows Support?!

For the first time, we have a Windows build in the downloads!

Note that you must have llvm-mingw with LLVM 15 installed and its \bin\ folder in the PATH for this to work. Then, running build.bat should produce a neat.exe that you can run.

Breaking change: the fail tuple attribute has been removed.
It was redundant with the Error class, which is supposed to be the superclass of every error class. For identical behavior, map the former fail type to breakelse with case.

The rest in v0.7.0 is mostly just small bugfixes.