Add pypy wheel building and publishing to Github actions workflow and Makefile

[LarsDu]

The biggest weakness of pyxel compared to other platforms like PICO-8 is the intrinsic slowness of python compared to languages like Lua which can leverage LuaJit.

The PyPy project leverages JIT, but not all python packages publish pypy wheels. Pyxel is one such project. This is my first pass attempt to alter the CI/CD pipeline to publish pypy wheels for the community to give users the option to leverage the speed of pypy.

Pyxel is a perfect candidate for leveraging pypy since most pyxel games will be completely self-contained and not necessarily need to bring in dependencies from the Cpython ecosystem.

When using package managers like uv switching the python backend to pypy should be as easy as putting [email protected] in the .python-version file.

I was able to run this CI pipeline myself to generate python wheels for pypy here. I successfully tested the pyxel-2.3.10-pp310-pypy310_pp73-win_amd64.whl wheel on a windows PC via uv pip install and it seems to work fine.

[LarsDu]

Was able to succesfully build some wheels: https://github.com/LarsDu/pyxel/actions/runs/13755037782

Was able to test out the windows x86 wheel and it works with pypy!