New package - libconeangle

[KjellJorner]

@everythingfunctional

In my experience, the GitHub Windows CI environment has gfortran 10.3 installed, and it’s possible to get 11.2 installed using msys. Also, I’ve had good luck with the installer provided by equation.com.

Yes, I am building Windows wheels on GitHub Actions. You can get the 11.2 just by running choco upgrade mingw. Conda-forge is stuck at 5.3 though.