Could you please add a `[build-sysem]` section to `pyproject.toml`?

[Richard Höchenberger]

Installing this project with pip (or another build frontend that's not poetry) doesn't work because poetry is not specified as the build backend in pyproject.toml. Would you consider adding this section to pyproject.toml? It is described in the poetry docs:

https://python-poetry.org/docs/pyproject/#poetry-and-pep-517

Thank you very much!

Richard