Add download purl2url support for bitbucket and gitlab #36

Job	Run time
Lint & mypy	20s
Test & build (py3.11 on ubuntu-latest)	17s
Test & build (py3.10 on ubuntu-latest)	14s
Test & build (py3.9 on ubuntu-latest)	21s
Test & build (py3.8 on ubuntu-latest)	17s
Test & build (py3.7 on ubuntu-latest)	21s
Test & build (py3.11 on windows-latest)	51s
Test & build (py3.10 on windows-latest)	49s
Test & build (py3.9 on windows-latest)	55s
Test & build (py3.8 on windows-latest)	1m 0s
Test & build (py3.7 on windows-latest)	59s
Test & build (py3.11 on macos-latest)	36s
Test & build (py3.10 on macos-latest)	26s
Test & build (py3.9 on macos-latest)	21s
Test & build (py3.8 on macos-latest)	26s
Test & build (py3.7 on macos-latest)	29s
	8m 42s

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