Investigate adding a license checker for built wheels

[threexc]

Right now, part of the wheel build review process has always involved downloading a built wheel, unpacking it, and inspecting it for:

1. The project's LICENSE files and related data
2. The presence of linked libraries included in the wheels as part of the final build process
3. Any license compliance steps which needed to be taken based on the libraries found in uvloop riscv64 support #2 (if any)

It would be very helpful to have this check automated along with everything else we've got running for every PR. However, while checking for the correct license according to the target project may be simple, having the workflow/script confirm that we aren't missing any supplemental licensing (or, possibly, that the wheels are actually failing to meet licensing requirements) is going to be more complicated.