v1.0.0

Main changes

• Improve documentation, and use the mkdocs-material theme
• mkdocs.yml changes. Enable dark/light modes from mkdocs-material
• Improved type hints, and add static type checks (mypy)
• Improve unit tests and add unit test code coverage reporting
• Manage the package using poetry; phase out setuptools.
• Apply some of the approaches in https://py-pkgs.org.
• Restore appveyor CI to a working state