[#73] Add documenation for the documentation styleguide.

[adiroiban]

Scope

Fixes #73

Changes

Add an initial page.

As a drive-by the theme was updated to Furo so that we have dart and light version.

Also, the project was updated to Python 3 and latest sphinx version.

How to try and test the changes

reviewers: @dumol @MohamedWasimMohamedAkram

check that changes make sense

Documentation preview here https://chevah-geck--89.org.readthedocs.build/styleguide/documentation.html

[adiroiban]

needs-review

[dumol]

Some minor improvements in my commit above. Please double-check, thanks!

Also, couldn't run ./pythia.sh deps on my musl-based workstation:

INFO: pip is looking at multiple versions of furo to determine which version is compatible with other requirements. This could take a while.
ERROR: Could not find a version that satisfies the requirement sphinx-basic-ng>=1.0.0.beta2 (from furo) (from versions: none)
ERROR: No matching distribution found for sphinx-basic-ng>=1.0.0.beta2

[adiroiban]

Thankd... not sure what is going on there

It looks like wants to install sphinx-basic-ng ... but this is missing for our pypi.

I have copied it.

BUt on my system, the deps for furo are:

Requirement already satisfied: Sphinx==7.3.7 in ./build/lib/python3.11/site-packages (from -r docs/requirements.txt (line 1)) (7.3.7)
Requirement already satisfied: furo in ./build/lib/python3.11/site-packages (from -r docs/requirements.txt (line 2)) (2024.5.6)
Requirement already satisfied: sphinxcontrib-applehelp in ./build/lib/python3.11/site-packages (from Sphinx==7.3.7->-r docs/requirements.txt (line 1)) (1.0.4)
Requirement already satisfied: sphinxcontrib-devhelp in ./build/lib/python3.11/site-packages (from Sphinx==7.3.7->-r docs/requirements.txt (line 1)) (1.0.2)
Requirement already satisfied: sphinxcontrib-jsmath in ./build/lib/python3.11/site-packages (from Sphinx==7.3.7->-r docs/requirements.txt (line 1)) (1.0.1)
Requirement already satisfied: sphinxcontrib-htmlhelp>=2.0.0 in ./build/lib/python3.11/site-packages (from Sphinx==7.3.7->-r docs/requirements.txt (line 1)) (2.0.1)
Requirement already satisfied: sphinxcontrib-serializinghtml>=1.1.9 in ./build/lib/python3.11/site-packages (from Sphinx==7.3.7->-r docs/requirements.txt (line 1)) (1.1.10)
Requirement already satisfied: sphinxcontrib-qthelp in ./build/lib/python3.11/site-packages (from Sphinx==7.3.7->-r docs/requirements.txt (line 1)) (1.0.3)
R

[dumol]

Thanks! I have deps working now on my system.

changes-approved