Upload artifacts to PyPI

[semiversus]

This pull requests uploads the already build packages for windows, linux and mac os to PyPI, so it will be possible to install PyOpTools simply by pip install pyoptools.

What needs to be done by pyoptools maintainers:

• Generate an API token at PyPI (https://pypi.org/help/#apitoken)
• Create a repository secret named "PYPI_API_TOKEN" with the retrieved API token as value (https://docs.github.com/en/actions/security-guides/encrypted-secrets#creating-encrypted-secrets-for-a-repository)
• As the current available version is 0.1.1 on PyPI you should update the version info in setup.py (maybe 0.2.0?)
• Every tagged version will be uploaded to PyPI. Create a tag via Github named like the version (e.g. "0.2.0")

Next steps (future pull requests):

• get the version information automatically based on the tag name
• cleanup project files to use a pyproject.toml based approach - everything is cleaner and easier

[semiversus]

Cool, thanks!