File an informational RFC for Blake3

[bkmgit]

Transferring this from BLAKE3-team/BLAKE3#347 created by @dralley

The OpenSSL project states that "a necessary condition to include a new algorithm into the main code base is that the algorithm should be part of a standard from a recognized standardization body", and also that "Informational RFCs are sufficient for adopting an algorithm by OpenSSL."

openssl/openssl#11613

It would be great to (eventually) see an implementation of Blake3 in OpenSSL, because that would open the door to it being included in places like the Python standard library. It seems like they might be open to it, but this would be a prerequisite.

As an example here is the informational RFC for Blake 2 https://www.rfc-editor.org/rfc/rfc7693.html