Add Cargo lock file

[psibi]

Since this package creates an executable, the recommendation is to check Cargo.lock as part of this repository.

Also, since I'm planning to package this as part of nixpkgs, it needs the Cargo lock file for ensuring reproducibility.

[psibi]

I have sent a PR packaging this for nixpkgs: NixOS/nixpkgs#131538

[vrmiguel]

Thanks a lot for packaging ouch for Nix! :-D

[psibi]

@vrmiguel Thanks for creating ouch. Also, it should be available as part of nixpkgs-unstable in a couple of days. :-)