Generate SBOM for shacl2code wheel

[bact]

Pitloom is considered usable now and can generated SBOM with "A" grade on https://kartben.github.io/spdx3_viz/

We may hook Pitloom into Hatchling build process, to generate shacl2code SBOM and put it inside the wheel, following PEP 770 recommendation.

[bact]

See the real-world generated SBOMs from Pitloom from these PyPI downloads:

• https://pypi.org/project/pitloom/#files
• https://pypi.org/project/licenseid/#files

Download any of the .whl file, unzip it, look in *.dist-info/sboms subdirectory, there will be a .spdx3.json SBOM file. Can try validate it with validator or inspect it with the online visualizer tool above.

[bact]

#140 is merged and test-sbom.yml is now test SBOM generation for every PR.

See for example,
https://github.com/JPEWdev/shacl2code/actions/runs/32283666106/job/96167992898#step:6:383

See the generated SBOM here https://github.com/JPEWdev/shacl2code/actions/runs/32283666106/artifacts/9376785121