Add Cargo.lock

[numinit]

Description

It's useful to have this so we don't need to manually keep track of it in hermetic build systems like nixpkgs.

See guidance at https://blog.rust-lang.org/2023/08/29/committing-lockfiles/.

To align with that starting point, cargo new will no longer ignore Cargo.lock for libraries as of nightly-2023-08-24.

Checklist

• Test suite updated with functionality tests
• Test suite updated with negative tests
• Rustdoc string were added or updated
• CHANGELOG and/or other documentation added or updated
• This is not a code change

Reviewer's checklist:

• Any issues marked for closing are fully addressed
• There is a test suite reasonably covering new functionality or modifications
• This feature/change has adequate documentation added
• A changelog entry is added if the change is significant
• Code conform to coding style that today cannot yet be enforced via the check style test
• Commits have short titles and sensible text
• Doc string are properly updated