Xxhash port in Rust

For my personal need I found xxhash to be optimal solution for hashing and so I made its Rust port https://github.com/DoumanAsh/xxhash-rust

Versioning follows original C implementation.
And provides const fn version of major algorithms.
Not all optimizations are included yet and I didn't implement xxh3 128 bit variant as I found little use cases for it.
Performance is closely matching C implementation (mostly because code is written in C style as original implementation). The only exception is xxh3 streaming variant which is pretty slow on small input.

Feedback is appreciated to make code more rust-like (not at expense of performance)