extend project URLs -> external references

[jkowalleck]

Is your feature request related to a problem? Please describe.

This tool detects project URLs and emits them in the SBOM results as "external references".
The URL types are detected based on patterns - see

cyclonedx-python/cyclonedx_py/_internal/utils/cdx.py

Lines 85 to 104 in 721f12d

	__known_ulr_labels: Dict[str, ExternalReferenceType] = {
	# see https://peps.python.org/pep-0345/#project-url-multiple-use
	# see https://github.com/pypi/warehouse/issues/5947#issuecomment-699660629
	'bugtracker': ExternalReferenceType.ISSUE_TRACKER,
	'issuetracker': ExternalReferenceType.ISSUE_TRACKER,
	'issues': ExternalReferenceType.ISSUE_TRACKER,
	'bugreports': ExternalReferenceType.ISSUE_TRACKER,
	'tracker': ExternalReferenceType.ISSUE_TRACKER,
	'home': ExternalReferenceType.WEBSITE,
	'homepage': ExternalReferenceType.WEBSITE,
	'download': ExternalReferenceType.DISTRIBUTION,
	'documentation': ExternalReferenceType.DOCUMENTATION,
	'docs': ExternalReferenceType.DOCUMENTATION,
	'changelog': ExternalReferenceType.RELEASE_NOTES,
	'changes': ExternalReferenceType.RELEASE_NOTES,
	# 'source': ExternalReferenceType.SOURCE-DISTRIBUTION,
	'repository': ExternalReferenceType.VCS,
	'github': ExternalReferenceType.VCS,
	'chat': ExternalReferenceType.CHAT,
	}

it appears that PyPI also documented the way they detect URL types: https://docs.pypi.org/project_metadata/#icons

It would be great if the PyPI heuristics could be applied, too.

Describe the solution you'd like

Have the heuristics from PyPI apply to URL type detections, so that emitted external references follow the de facto standards, too.

These heuristics work on the URL name, as well on the URL itself.

Additional context

PyPI's type classification according to https://docs.pypi.org/project_metadata/#icons