skpkg: pdffit2 up to scikit-package 0.1.0 standards

[cadenmyers13]

closes #134
ran the examples and everything works! pytest passes and the docs render properly.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.97%. Comparing base (94b53fc) to head (edc5bd0).
Report is 25 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #140   +/-   ##
=======================================
  Coverage   98.97%   98.97%           
=======================================
  Files           6        6           
  Lines        1267     1267           
=======================================
  Hits         1254     1254           
  Misses         13       13           

Files with missing lines	Coverage Δ
tests/test_exceptions.py	99.80% <100.00%> (ø)
tests/test_pdffit.py	99.76% <100.00%> (ø)
tests/test_phase_fractions.py	98.70% <100.00%> (ø)
tests/test_shape_factors.py	99.53% <100.00%> (ø)

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[sbillinge]

super! Please can you update mission-control?