Add faster Gamma

[rohanbabbar04]

Description

• Add class Gamma with all methods
• Add test in test_scipy.py.
• Update docs

Checklist

• Code style is correct (follows pylint and black guidelines)
• Includes new or updated tests to cover the new feature
• New features are properly documented (with an example if appropriate)

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 94.79167% with 5 lines in your changes are missing coverage. Please review.

Project coverage is 81.68%. Comparing base (a7887ea) to head (7d9bfe0).
Report is 3 commits behind head on main.

Files	Patch %	Lines
preliz/distributions/gamma.py	94.73%	5 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #387      +/-   ##
==========================================
- Coverage   83.66%   81.68%   -1.99%     
==========================================
  Files          64       68       +4     
  Lines        5842     6175     +333     
==========================================
+ Hits         4888     5044     +156     
- Misses        954     1131     +177     

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[rohanbabbar04]

One of my test in test_maxent is failing, I have commented it as of now

Any idea why is this happening?

[aloctavodia]

The expression for the entropy was not correct, although it could return values close to the correct ones.

[rohanbabbar04]

The expression for the entropy was not correct, although it could return values close to the correct ones.

Thanks, noted I forgot we have digamma already implemented in our preliz.internal.special