Add JOSS reference

[bhazelton]

Description

Add citation information for our JOSS paper to the readme.

Motivation and Context

Checklists:

Documentation Change Checklist:

• I have read the contribution guide.
• My code follows the code style of this project.
  Documentation change checklist:
• Any updated docstrings use the numpy docstring format.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00%. Comparing base (88932f3) to head (4c10c73).
Report is 25 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##              main      #247   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            5         5           
  Lines         2131      2131           
  Branches       608       608           
=========================================
  Hits          2131      2131           

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[jpober]

This looks great, so I approve. But tests are failing and I can never keep track of when that's expected and when that's not...