Add Julia type and tests

[Octogonapus]

This PR adds a Julia type, along with some tests based on the provided examples.

cc package-url/packageurl-go#44

[g-sahil22]

We have generated the SBOM using PkgToSoftwareBOM.jl tool, but in that tool, PURL is missing, so I want to know can I use PURL Spec mentioned in the commit to generate the PURLs

There is one package repo available for Julia https://juliahub.com/ui/Home

[Octogonapus]

I have used this spec to implement aquasecurity/trivy#5635. Without further review from the maintainers of this organization, I would just assume this spec is sufficient and use it for whatever you need.

[g-sahil22]

Hi @Octogonapus , I have tried trivy to generate SBOM for an Open-Source Julia project, but in the SBOM I didn't report any components

[Octogonapus]

Let's move the discussion to aquasecurity/trivy#5635
Also you will need to tell me which julia project, and keep in mind you need to build trivy from source using my PR