Zcash-flavored Ed25519 for use in Zebra.

Zcash uses Ed25519 for JoinSplit signatures with particular consensus-critical validation rules. These rules are not part of the Ed25519 specification in RFC8032, which does not specify the set of valid Ed25519 signatures and does not require conformant implementations to agree on whether a signature is valid. Because the Zcash-flavored validation rules are consensus-critical, Zebra requires an Ed25519 library that implements the Zcash-flavored validation rules specifically, which this crate provides.