Files for setup a package and release is missing

[Ludee]

Description of the issue

The option to include a setup.py is deprecated.
Instead it is recommended to include a pyproject.toml.

Ideas of solution

Look for similar projects and include a working file.
It is connected to #11

Sources:

• https://pip.pypa.io/en/stable/reference/build-system/pyproject-toml/
• Replace setup.py by pyproject.toml joaomcteixeira/python-project-skeleton#33
• https://github.com/oemof/oemof-solph/blob/dev/pyproject.toml

Workflow checklist

• I am aware of the workflow in CONTRIBUTING.md