Consider auto-running clippy on commit

[david-allison]

For discussion

Note: this did produce unexpected formatting, so fmt was necessary

cargo clippy --fix --allow-dirty --allow-staged
cargo fmt

[mikehardy]

works for me, it's possibly heavy but...if it's not in pre-commit it'll likely not be run

should be check-rust.sh or .bat though I think, so all our learnings are encapsulated (like, you have to run fmt, and you need to set the environment variable to make warnings errors etc)

also, there was all that work in Anki-Android repo about preserving staged files on failure, apparently that can be a problem