Move to under moby org

[kolyshkin]

As discussed with @thaJeztah, this repo needs to be move to under moby, i.e. become github.com/moby/go-units.

[thaJeztah]

@justincormack can you help with this? (Unless you have objections against moving it of course)

It's a small utility project, used in a couple of projects, and it felt like one of those "not really a Docker, inc. product thing", so suitable for Moby org (and adding common maintainers)

[thaJeztah]

(moving should be generally safe; initially we can rely on the github redirects; after that we can rename the imports / module)

[kolyshkin]

@justincormack please 🙏🏻

[thaJeztah]

Got a short reply from @justincormack, but no "answer" yet 😅