devel/libblake3: New port: C library providing BLAKE3

C library providing BLAKE3 hash function.

BLAKE3 is a cryptographic hash function that is:

 - Much faster than MD5, SHA-1, SHA-2, SHA-3, and BLAKE2.

 - Secure, unlike MD5 and SHA-1. And secure against length
   extension, unlike SHA-2.

 - Highly parallelizable across any number of threads and
   SIMD lanes, because it's a Merkle tree on the inside.

 - Capable of verified streaming and incremental updates,
   again because it's a Merkle tree.

 - A PRF, MAC, KDF, and XOF, as well as a regular hash.

 - One algorithm with no variants, which is fast on x86-64
   and also on smaller architectures.