Support package type specific diff

[prabhu]

Consider the attached bom files

This includes packages of type debian and npm.

bom-docker.json

The below two only include packages of type npm
bom-pre-build-reqonly.json
bom-pre-build.json

When computing the diff, there could be an option to first group based on the package type and compute type specific diffs in addition to aggregate diffs. This way we can identify the exact common npm libraries and frameworks, and net new additions.
diff-htmls.zip