Save build requirements into pyproject.toml

[markotoplak]

Issue

There was a PEP-517 warning before:

python setup.py bdist_wheel
/home/marko/venv310/lib/python3.10/site-packages/setuptools/__init__.py:94: _DeprecatedInstaller: setuptools.installer and fetch_build_eggs are deprecated.
!!

        ********************************************************************************
        Requirements should be satisfied by a PEP 517 installer.
        If you are using pip, you can try `pip install --use-pep517`.
        ********************************************************************************

This makes it disappear.