The old `cargo-3ds` we were using didn't care about the commit date being 05-30, but the new one used by the `test-runner` action does.
Since the rustc version is one day older than the toolchain date, we should be able to work with just the 06-01 toolchain instead.
- Add a helper for local testing with https://github.com/nektos/act
- Don't deny clippy warnings, they can change too easily and break CI
- Add minimum rust version just for completeness' sake
Ian Chamberlain