Adding glossary + refactor API reference display

[quentinblampey]

• Adding a glossary to the docs
• Updating docs display (sections on the left, functions on the right)
• Adding docstrings to all functions missing docstrings

@LucaMarconato actually the issue I had with some functions not being displayed in the docs is because they were not documented. This is mostly for the transformations (MapAxis, Affine, ...) and the models. Should we document everything or keep it like that? Meanwhile, I added :undoc-members: so that methods with no docs are still displayed.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.84%. Comparing base (27bb4a7) to head (561bfb8).
Report is 12 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #785      +/-   ##
==========================================
- Coverage   91.89%   91.84%   -0.05%     
==========================================
  Files          45       45              
  Lines        6919     6893      -26     
==========================================
- Hits         6358     6331      -27     
- Misses        561      562       +1     

Files with missing lines	Coverage Δ
src/spatialdata/_core/query/spatial_query.py	95.46% <ø> (-0.02%)	⬇️
src/spatialdata/transformations/transformations.py	94.61% <ø> (ø)

... and 28 files with indirect coverage changes