metadata for pypi distribution

[peppelinux]

This pull request introduces improvements to the packaging and publishing workflow for the pymdoccbor project. The main changes include adding a pyproject.toml file to specify build system requirements, introducing a new script to automate publishing to PyPI, and updating the license field in setup.py for better standards compliance.

Packaging and build system updates:

• Added a pyproject.toml file specifying setuptools as the build backend and minimum version required, ensuring compatibility with modern Python packaging tools.

Publishing automation:

• Introduced a new script scripts/publish_pypi.sh to automate building and publishing the package to PyPI or TestPyPI, including dry-run and build-only modes, and improved dependency handling for publishing.

Metadata improvements:

• Updated the license field in setup.py from a classifier string to the SPDX identifier "Apache-2.0" for better standards compliance.