feat(julia): Add license detection for Julia

[Octogonapus]

Description

Add license detection for Julia packages.

This is incomplete, I will add tests where needed and remove extraneous code before marking this PR as ready. First I am asking for some maintainer feedback:

Julia packages often don't specify their license in their Project.toml file (even though they should). I've included some rudimentary content-based license detection to help with that because I'm not sure if this project would accept adding a dependency for this. There are some dependencies (e.g. licensecheck and go-license-detector) which do a better job. What do you think about adding a dependency for license detection?

Checklist

• I've read the guidelines for contributing to this repository.
• I've followed the conventions in the PR title.
• I've added tests that prove my fix is effective or that my feature works.
• I've updated the documentation with the relevant information (if needed).
• I've added usage information (if the PR introduces new options)
• I've included a "before" and "after" example to the description (if the PR is a user interface change).