Adds support for mkdocs

[sebastian-quintero]

Description

Adds a new way of documenting the Python SDKs with:

• MkDocs: https://www.mkdocs.org
• mkdocstrings-python: https://mkdocstrings.github.io/python/
• Material for MkDocs: https://squidfunk.github.io/mkdocs-material/
• ReadTheDocs for free hosting (for now): https://about.readthedocs.com

• Heavily edits the docstrings of the entire project across all Python files.
• Adds the new docs dir with all the source of the docs in .md.
• Copies over all the docs we had from the docs site to here, in the form of "Tutorials".
• Introduces the technical "Reference" with the documentation of the Python modules, classes, functions, methods, etc.

To serve the documentation locally:

• Install the requirements.

$ pip install docs/requirements.txt

• Serve.

$ mkdocs build && mkdocs serve