Adding a pyproject.toml to ensure compliance with updates to pip

[tg1482]

Getting this warning while installing

 DEPRECATION: Flask-APScheduler is being installed using the legacy 'setup.py install' method, because it does not have
 a 'pyproject.toml' and the 'wheel' package is not installed. pip 23.1 will enforce this behaviour change. A possible
 replacement is to enable the '--use-pep517' option. Discussion can be found at https://github.com/pypa/pip/issues/8559