update readme examples to match docs

[noahsong-sdg]

A small fix to the Hamiltonians in the repo readme. Updated them to match the source model Hamiltonians and documentation.

[phjmsycc]

Closes #81

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.00%. Comparing base (43d4edb) to head (0521f3b).
⚠️ Report is 8 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #82   +/-   ##
=======================================
  Coverage   90.00%   90.00%           
=======================================
  Files          18       18           
  Lines        2172     2172           
=======================================
  Hits         1955     1955           
  Misses        217      217           

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