Implementation of Maxwell Distribution

[tvwenger]

What is this PR about?
This PR implements the Maxwell distribution following this discussion and this related PR, which implements the Maxwell RV in pytensor. Maxwell distribution appears often in physical systems and having access to it in pymc and pytensor would be generally useful.

I have attempted to follow the style of other similarly-implemented distributions, and I have included the relevant docstrings and tests.

I attempted to run tests/distributions/test_continuous.py before submitting this PR, but I received an error that seems to be irrelevant to these changes.

Checklist

• Explain important implementation details 👆
• Make sure that the pre-commit linting/style checks pass.
• Link relevant issues (preferably in nice commit messages)
• Are the changes covered by tests and docstrings?
• Fill out the short summary sections 👇

Major / Breaking Changes

• None

New features

• Implementation of the Maxwell distribution

Bugfixes

• None

Documentation

• Included docstrings as necessary

Maintenance

• N/A

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📚 Documentation preview 📚: https://pymc--6907.org.readthedocs.build/en/6907/

[welcome]

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[tvwenger]

Since this implementation depends on the pytensor PR, I don't really know the proper protocol/testing relationship. Any help would be appreciated!

[tvwenger]

I was also confused about how to implement test_maxwell_moments, so any help there would be appreciated as well!

[ricardoV94]

@tvwenger please open this PR on pymc-experimental.

Let me know if the suggestion to use a CustomDist in the original discussion sounds correct.

[tvwenger]

Related PR on pymc-experimental: pymc-devs/pymc-extras#239