…t more platforms

This changes the GitHub action to use cibuildwheel tool to build the wheels, was using manylinux docker instead. By moving to the more generic cibuildwheel, the concrete platform-specific steps to build wheels are encapsulated. This introduction allows building wheels for more os a lot easier (support is TODO). As a side effect, pypy wheels are now built.

Second part is to use the GitHub action for publishing to pypi from pypa with simplification to the checking logic.