Missing license

[h-vetinari]

We don't have a license file in this repo. @aktech also mentioned that we should add a copy/reference to https://github.com/actions/runner-images/blob/main/LICENSE (compatible because MIT), since the setup in #145 was apparently inspired by that (and I'll also need it to add compilers for #168).

Should we use the regular BSD-3 license as a baseline that we also use for regular feedstocks?

CC @jaimergp

[jaimergp]

Sure, let's add it.

[h-vetinari]

"it" being: BSD-3 for the general repo, as well as the MIT license from the runner-images repo?

[jaimergp]

I think that's what we need to do, yes, but IANAL.

[jakirkham]

If it was already under MIT, it seems fine to keep it under MIT

Normally we BSD-3-Clause in conda-forge, but it makes sense to be practical here and stick with the original licensing

[h-vetinari]

Not all of the code here is from runner-images, only the recently-added stuff to build the custom windows VMs we need for cirun. All the rest also needs a license. I'd be fine to reuse MIT for that though, that avoids having to do two separate licenses.