Add Cargo.lock to repository

[jirutka]

Can you please add Cargo.lock to the repository and keep it up to date for releases? It’s needed for reproducible builds, which is especially important for Linux distributions. With no lockfile, cargo fetches the latest version of the dependencies that satisfy the version constraint, so you may get a different binary when it’s built a week later.

[ChuckHend]

@jirutka , thanks for raising the issue! Closing this now, but will re-open if you think #39 did not address the need.