ClassGraphic initial public release

Full Changelog: https://github.com/dionresearch/classgraphic/commits/v0.2.0

0.2.0 (2022-09-18)

The previous version was a first step to doing a public release. This
release added:

• documentation
• updated the code to be in line with plotly 5.x

It was released to github and pypy.

Note: this requires Python 3.8 or later. We use Numpy which already requires 3.8 (https://numpy.org/neps/nep-0029-deprecation_policy.html) and scikit-learn also requiring python 3.8 (https://scikit-learn.org/stable/install.html). Similar story with Pandas (https://pandas.pydata.org/docs/getting_started/install.html). The ClassGraphic code base thus assumes Python 3.8 from a syntax point of view and will not work with Python 3.7 or older.