ensure extension modules are present in built wheel

[zacharyburnett]

Resolves SCSB-149

Checklist

• added entry in CHANGES.rst (either in Bug Fixes or Changes to API)
• updated relevant tests
• updated relevant documentation
• updated relevant milestone(s)
• added relevant label(s)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 84.99%. Comparing base (af5aefb) to head (ccbc897).
Report is 5 commits behind head on main.

❗ Current head ccbc897 differs from pull request most recent head 216c0a7

Please upload reports for the commit 216c0a7 to get more accurate results.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #256      +/-   ##
==========================================
- Coverage   85.18%   84.99%   -0.19%     
==========================================
  Files          35       35              
  Lines        6797     6865      +68     
==========================================
+ Hits         5790     5835      +45     
- Misses       1007     1030      +23     

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[zacharyburnett]

after merging #156, add its module to the test command:

Suggested change

	test_command: python -c "from stcal.ramp_fitting.ols_cas22 import _ramp, _jump, _fit"
	test_command: python -c "from stcal.ramp_fitting.ols_cas22 import _ramp, _jump, _fit; from stcal.ramp_fitting import slope_fitter"