Check in Cargo.lock?

It'd be helpful to have a Cargo.lock file checked into the repo. Primarily, this would let users be confident that they're using the same dependency versions you've tested with, using `cargo install --locked faketty`. It's also helpful for OS/packager use cases, where you sometimes need to fetch dependencies first, then build offline; I'm currently generating a lockfile and checking it in, as a workaround, but smarter tooling could use a lockfile upstream.

Thanks for the great tool!