`setup.py` superseded by `pyproject.toml`

[peanutfun]

setup.py was generally superseded by the safer pyproject.toml. This package provides the latter. Couldn't setup.py be removed?

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I raise this issue as part of my review in openjournals/joss-reviews#9439

[hkershaw-brown]

I will double check this, but I the setup.py was needed for editable installs.