Add optional ax argument to CLV plot utilities

[wd60622]

Closes #342

[wd60622]

Docs render a bit better now

https://pymc-marketing--344.org.readthedocs.build/en/344/api/generated/pymc_marketing.clv.plotting.plot_probability_alive_matrix.html#pymc_marketing.clv.plotting.plot_probability_alive_matrix

[codecov]

Codecov Report

Merging #344 (071b070) into main (12b56e2) will increase coverage by 0.13%.
The diff coverage is 14.28%.

@@            Coverage Diff             @@
##             main     #344      +/-   ##
==========================================
+ Coverage   95.85%   95.98%   +0.13%     
==========================================
  Files          19       19              
  Lines        1447     1446       -1     
==========================================
+ Hits         1387     1388       +1     
+ Misses         60       58       -2     

Files Changed	Coverage Δ
pymc_marketing/clv/plotting.py	16.27% <14.28%> (+2.64%)	⬆️

[juanitorduz]

🙌

[ricardoV94]

Thanks @wd60622