What would you like to be added:

Syft requires to do "docker login" first for private registries. But what if I don't have a docker CLI installed on my environment? In this case, I should be able to log in with syft. So, we (w/@Dentrax) are proposing to add a new login command for Syft, actually, it is so easy to add¹. Because crane has some global commands that we can easily use.

https://github.com/google/ko/blob/8e4587e93e309f615482e97d3ec5a402dd263b8c/pkg/commands/root.go#L60

Why is this needed:

Additional context: