feat: add stub for BUSL-1.1

[spiffcs]

Notes

This adds basic coverage to license check to discover the BUSL as described by HASHICORP. I think the LRE can be written a bit more generically so we can capture the parameters and have a higher confidence match, but this is a first pass. We also have the option of adding a URL discovery option as well which I'm looking into.

The test case for this was awkward to write since the README specified that a test case could have the header:

90.5%
BSD 98.9% 1234,4567 [URL]

When I included the second percent which I assumed was a percent coverage for the offset the test would error and show that it only expected: BSD 1234,4567 [URL] as a valid case entry.

If this is incorrect and there is some other configuration where I can test the %coverage of the whole case along withthe %coverage of the offset I would like to set it up that way.

[spiffcs]

We want to get this percentage up before merging. This was the base case where I could get the LRE matching on everything under the hashicorp parameters