Add back MacOS CI testing

[cmalinmayor]

Proposed Change

Closes #26, using Talley's detective work:
#25 (comment)

Checklist

Go through these things before merge. Actions should run automatically to test them, but for information on how to run locally, see CONTRIBUTING.md.

• I have added tests that prove that my feature works in various situations or tests the bugfix (if applicable).
• I have checked that the tests pass and I maintained or improved test coverage (if applicable).
• I have written docstrings and checked that they render correctly in the documentation build.

[codecov-commenter]

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