DOC: Add rcParams defaults and descriptions to documentation (#2457)

[pranavkp71]

This PR adds a complete table of all ArviZ rcParams, including their default
values and short descriptions, based on the definitions in arvizrc.template.

This improves the documentation page at rcParams by listing all available
configuration keys in a clear and accessible way.

Fixes #2457.

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📚 Documentation preview 📚: https://arviz--2496.org.readthedocs.build/en/2496/

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 86.81%. Comparing base (4db6129) to head (2e0df90).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2496      +/-   ##
==========================================
- Coverage   86.84%   86.81%   -0.04%     
==========================================
  Files         124      124              
  Lines       13036    13036              
==========================================
- Hits        11321    11317       -4     
- Misses       1715     1719       +4     

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[pranavkp71]

Hi @OriolAbril and @williambdean,

I think the failing tests are unrelated to this docs-only change.
BaseTests and the documentation build succeeded.

If anything is needed from my side, please let me know. Thanks