Create "Read the Docs" webpage

[MarcSerraPeralta]

Use "Read the Docs" and Sphinx to create a webpage with the documentation. Sphinx allows to show plots in the documentation (as well as equations) which is helpful to see how the PDFs look like. ReadtheDocs can host the Sphinx documentation in a website, which is easier to read than through github.

TODO

• [x] Add docs badge to repo (can be found in readthedocs)
• [x] Update all docs in repo using numpy style: https://sphinxcontrib-napoleon.readthedocs.io/en/latest/example_numpy.html
• [x] Move the .md doc files to the documentation
• [x] Solve problem with links in plots module
• [x] Use experimental data for the plots in the classifiers' documentation
• [x] Add plot example and link to API for the 3-state classifier gmda
• [x] Add descriptions to the modules (if necessary)
• [x] Add github logo at the top right of the website

[MarcSerraPeralta]

Find here a tutorial on how to use Sphinx to document a repo and how to publish it in ReadtheDocs:

https://sphinx-rtd-tutorial.readthedocs.io/en/latest/index.html