Add BLAKE3 implementation

[saucecontrol]

xoofx making me look bad over here

[viktor-svub]

Not exactly a fair comparison, is it -- as theirs is just a thin .NET wrapper over an unmanaged library -- which I'd rather avoid :)

[saucecontrol]

Now that we have access to SIMD intrinsics in .NET I consider everything fair 😄

But yeah, I'd rather have a managed implementation as well, and it will be fun to see if I can beat the Rust version on perf (at least up to AVX2).

[egbakou]

@saucecontrol You can find the BLAKE3 implemented here https://github.com/xoofx/Blake3.NET by @xoofx