Add plot_ppc_pit

[aloctavodia]

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📚 Documentation preview 📚: https://arviz-plots--159.org.readthedocs.build/en/159/

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 12.22222% with 79 lines in your changes missing coverage. Please review.

Project coverage is 74.38%. Comparing base (8e4294e) to head (d24239c).

Files with missing lines	Patch %	Lines
src/arviz_plots/plots/ppcpitplot.py	11.23%	79 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #159      +/-   ##
==========================================
- Coverage   75.93%   74.38%   -1.55%     
==========================================
  Files          30       31       +1     
  Lines        3611     3701      +90     
==========================================
+ Hits         2742     2753      +11     
- Misses        869      948      +79     

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