blake2b-rs wasm test

This test is loosely based on the Mozilla's guide: Compiling from Rust to WebAssembly

To run these tests:

• Install Rust and Clang then
• cargo install wasm-pack;
• cargo build; //Ok
• cargo build --target wasm32-unknown-unknown; //fatal error: 'string.h' file not found

This error is related to: Status of rust+C bindings for wasm targets