refactor: decouple license detection logic

[nscuro]

Addresses #117

[nscuro]

@imjasonh I went with decoupling the code using go-license-detector into a different package. Different module would be nice, but I don't see myself dealing with multiple modules at this point. As you noted in #100, it becomes fairly unwieldy.

Means this will only address your binary size concerns, but not the potential issue of tooling complaining about modules you're not consuming. I'm leaning towards blaming the tooling for this though. 😄

Either way, as expected, the current solution will reduce the binary size by a little over 4mb:

Would this be a compromise you're willing to take?