Fix readme to make releases possible

[flying-sheep]

The release workflows currently fail with

 Checking dist/sklearn_ann-0.1.1-py3-none-any.whl: FAILED
ERROR    `long_description` has syntax errors in markup and would not be        
         rendered on PyPI.          

https://github.com/scikit-learn-contrib/sklearn-ann/actions/runs/8285153041/job/22672248085

maybe we simply missed adding readme = "README.rst" in pyproject.toml?

[flying-sheep]

Fixed in #25! It’s now published https://pypi.org/project/sklearn-ann/

@frankier if you tell me you PyPI name, I can add you as maintainer

[frankier]

Great! It's frankier.

Thanks for the continued poking and pushing all this through.

[flying-sheep]

done!