Add cargo check rust action

[marcustyphoon]

This adds a github action that runs the Rust linter on the Rust module, including tests/benches. (I didn't check if warnings make the action report success or failure; will have to test that).

Note that apparently the [lints] entry in Cargo.toml, similar to an eslint config in package.json, is not yet available in stable Rust: https://www.reddit.com/r/rust/comments/13re6rr/you_can_specify_lints_with_lints_table_in/

Thus, it looks like the best way to turn off rules at the moment is via #![allow(rulename)] at the top of lib.rs.

• Make this succeed

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[marcustyphoon]

apparently I have to merge this to get the action to run to test it!