Add a CC-BY-4.0 and name it LICENSE

[nsryan2]

Summary of changes

This PR adds a CC-BY-4.0 license to this repository.

Types of changes

• [ ] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)
• [ ] I have read the CONTRIBUTING document.
• [x] My code follows the code style of this project.
• [ ] My change requires a change to the documentation.
• [ ] I have updated the documentation accordingly.
• [ ] I have added tests to cover my changes.
• [ ] All new and existing tests passed.

Associated Issues and PRs

• Issue: #81
• Issue: arfc/arfc.github.io#159

Checklist for Reviewers

Reviewers should use this link to get to the Review Checklist before they begin their review.

[Dayvis7]

@nsryan2 is this pretty much just copy and pasting what's on https://creativecommons.org/licenses/by/4.0/legalcode ?

[nsryan2]

Yeah, it's an international creative commons license with the attribution clause.