Consider publish `Cargo.lock` for better downstream packaging work.

[Vanilla]

I'm packaging pbpctrl for nixpkgs(https://github.com/NixOS/nixpkgs),
which need Cargo.lock file for deterministic build, otherwise we can only store lock in our repo.
I think publish lock file as author is a better choice : )

[Maximilian Luz]

I've added the Cargo.lock file.