feat: load BMA models

[ReubenJ]

This PR adds functionality to load and save to BioModelAnalzyer's format. We include two toy models that come from the BioModelAnalzyer test suite. We'll use them here to test loading and saving to the BMA tool's format.

Checklist

• I am following the contributing guidelines
• Tests are passing
• Lint workflow is passing
• Docs were updated and workflow is passing

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.40%. Comparing base (374e88d) to head (0e8788d).
⚠️ Report is 9 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #38      +/-   ##
==========================================
+ Coverage   97.89%   98.40%   +0.51%     
==========================================
  Files           2        3       +1     
  Lines         190      251      +61     
==========================================
+ Hits          186      247      +61     
  Misses          4        4              

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