No function to encode/decode signatures with recovery byte from Uint8Array#134

Presently `SignatureWithRecovery` only exposes `fromCompact` and `toCompactBytes` methods, so there's no out-of-the-box way to consume 65byte Ethereum signatures that come with the recovery byte at the end other than twiddling some bytes manually. I'm happy to submit a PR for this, but just figured I'd check if there was a rationale for excluding it before I do so