Add license file metadata to pyproject.toml

[bkmgit]

Feature Description

This is specified in pep 639 see:

https://packaging.python.org/en/latest/guides/licensing-examples-and-user-scenarios/
https://packaging.python.org/en/latest/specifications/core-metadata/#license-file-multiple-use

Problem and Solution

Enables easier identification of the license file.

Additional Context

No response

Are you willing to contribute to the development of this feature?

• Yes, I am willing to contribute to the development of this feature.