Updated docs and minor fixes to density_advanced

[charliematteo]

• updated docs with current modules structure, including density_advanced and neigh_graph -minor fixes to density_advanced

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 83.33333% with 1 line in your changes missing coverage. Please review.

Project coverage is 81.79%. Comparing base (24c4c60) to head (28d87d4). Report is 34 commits behind head on main.

Files	Patch %	Lines
dadapy/density_advanced.py	83.33%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #135 +/- ## ========================================== + Coverage 80.66% 81.79% +1.13% ========================================== Files 20 20 Lines 3330 3323 -7 ========================================== + Hits 2686 2718 +32 + Misses 644 605 -39 ```

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