Proper documentation

[AngryMaciek]

Move the docs into GH Pages or ReadTheDocs, change md to rst; use sphinx; add CI and README shield, add proper code comments.

[AngryMaciek]

After the documentation is built and we have an URL: add a link to PyPI and conda pages.

[AngryMaciek]

This might be a good place to start:
https://tech.michaelaltfield.net/2020/07/18/sphinx-rtd-github-pages-1/

[AngryMaciek]

read:

• https://docs.readthedocs.io/en/stable/intro/getting-started-with-sphinx.html
• https://www.writethedocs.org/guide/writing/beginners-guide-to-docs/#id1
• https://www.sphinx-doc.org/en/master/usage/restructuredtext/basics.html
• https://matplotlib.org/sampledoc/
• https://docs.python-guide.org/writing/style/#code-style
• https://realpython.com/documenting-python-code/
• https://www.ericholscher.com/blog/2016/jul/1/sphinx-and-rtd-for-writers/
• https://techwritingmatters.com/documenting-with-sphinx-tutorial-intro-overview
• https://www.sphinx-doc.org/en/master/usage/quickstart.html

[AngryMaciek]

TODO

• toctrees styling: broken alignment for captions in toctrees in ver. 0.5.1 readthedocs/sphinx_rtd_theme#1112 (comment)
• clean URLs?
• Changelog markdown parsing & include with toc subsections
• add main picture to the mainpage: https://stackoverflow.com/questions/66969914/sphinx-documentation-custom-images-dir-and-static-directory-for-html-docs
• wrap license text: https://stackoverflow.com/questions/66971299/sphinx-documentation-with-readthedocs-theme-text-block-wrapping | Sphinx docs with ReadTheDocs theme: custom css not included into the html after build sphinx-doc/sphinx#9090
• example results section
• search page (removed): Search page empty readthedocs/sphinx_rtd_theme#998
• bg section
• add old docs
• create docs section with API
• Module index section - not found? https://stackoverflow.com/questions/13838368/no-generation-of-the-module-index-modindex-when-using-sphinx Solution described here: https://samnicholls.net/2016/06/15/how-to-sphinx-readthedocs/

[AngryMaciek]

• Finish this issue with 1.0.39, publish new version to Zenodo too? clean the CHANGELOG! Update project's homepage in other resources too!
• binder: pkg version update!
• clean gh pages branch!