Replace setup.py with pyproject.toml

[Russell-Jones-OxPhys]

On installing, the message

DEPRECATION: Building 'untokenize' using the legacy setup.py bdist_wheel mechanism, which will be removed in a future version. pip 25.3 will enforce this behaviour change. A possible replacement is to use the standardized build interface by setting the --use-pep517 option, (possibly combined with --no-build-isolation), or adding a pyproject.toml file to the source tree of 'untokenize'. Discussion can be found at pypa/pip#6334

is displayed. It looks like this package has no dependencies, so can build in isolated mode with the following pyproject.toml . The linked bug gives a fuller explanation.

[build-system]
requires = ["setuptools >= 42.0.0"]
build-backend = "setuptools.build_meta"