Attempt to fix broken package automation.

Add GitHub action to do MyPy type check.

Add automated deployment to PyPI.

Bump minor version for new feature, update the README slightly.

Add ZiX-12A support.

v2.0.0: ZiX-12B full support, fixes, restructure.

Add support for ALT-1.0 archives, and help for ZiX-12B archives.

Avoid making the same check twice.

Resolve Lattyware#8: Replace optparse with argparse.

Resolve Lattyware#7