[Documentation] Make documentation reachable via web

[hearot]

Describe the issue
The built-in PyDoc is a great tool to explore documentation when you don't have an Internet connection, but it is poor, minimal. Tools like Sphinx, instead, give the user more readability and confidence.

Expected behavior
Make the documentation public using Sphinx and services such as Read the Docs.

Additional context
This issue contains an idea that was provided by #1 in the first place.

[hearot]

In order to make the documentation compliant with Sphinx specifications, fixes have to be applied (e.g. do follow Sphinx instructions to refer to methods).