Add rustix

[joshka]

Fixes: #135

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Crate description from readme:

rustix provides efficient memory-safe and I/O-safe wrappers to POSIX-like, Unix-like, Linux, and Winsock syscall-like APIs, with configurable backends. It uses Rust references, slices, and return values instead of raw pointers, and I/O safety types instead of raw file descriptors, providing memory safety, I/O safety, and provenance. It uses Results for reporting errors, bitflags instead of bare integer flags, an Arg trait with optimizations to efficiently accept any Rust string type, and several other efficient conveniences.

Simplified description for this PR:

Efficient and safe POSIX / *nix / Winsock syscall-like APIs. It uses idiomatic Rust types: refs, slices, Results instead of raw pointers, safe wrappers around raw file descriptors, bitflags instead of bare integer flags, and several other conveniences.

Perhaps add some opinion-sauce to this if needed.