Standalone implementation of Skyscraper 2-to-1 hash function for BN254 scalar field elements. See full paper at https://eprint.iacr.org/2025/058.pdf Implementation assumes each field element is represented as an array of four u64. Implememtation is optimized for a 64b CPU assuming it is executed on a single thread (not using SIMD). Top function is compress(). To run the benchmark type "cargo bench".