deprecate: addContribution deprecation

[cadenmyers13]

Deprecate FitRecipe.addContribution. Dont merge until upstream v4.0.0 branch has been made.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 69.65%. Comparing base (8db7cc6) to head (bc0ce35).
⚠️ Report is 18 commits behind head on v3.3.0.

Additional details and impacted files

@@            Coverage Diff             @@
##           v3.3.0     #147      +/-   ##
==========================================
+ Coverage   69.36%   69.65%   +0.28%     
==========================================
  Files          25       25              
  Lines        3457     3490      +33     
==========================================
+ Hits         2398     2431      +33     
  Misses       1059     1059              

Files with missing lines	Coverage Δ
tests/conftest.py	91.48% <100.00%> (ø)
tests/test_fitrecipe.py	99.78% <100.00%> (+0.01%)	⬆️

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[cadenmyers13]

@sbillinge ready for review. see PR message first