chore: migrate build setup from setuptools to build

[mxschmitt]

This addresses:

DEPRECATION: Legacy editable install of pytest-playwright==0.0.post1+g4912164 from file:///home/runner/work/playwright-pytest/playwright-pytest (setup.py develop) is deprecated. pip 25.0 will enforce this behaviour change. A possible replacement is to add a pyproject.toml or enable --use-pep517, and use setuptools >= 64. If the resulting installation is not behaving as expected, try using --config-settings editable_mode=compat. Please consult the setuptools documentation for more information. Discussion can be found at https://github.com/pypa/pip/issues/11457