* Moving `DecodeSegement` to `Parser`
This would allow us to remove some global variables and move them to parser options as well as potentially introduce interfaces for json and b64 encoding/decoding to replace the std lib, if someone wanted to do that for performance reasons.
We keep the functions exported because of explicit user demand.
* Sign/Verify does take the decoded form now
* accept generic crypto.Signer in ed25519 in order to allow usage of other ed25519 providers than crypto/ed25519
* add check to ensure the key is indeed of type ed25519
* adding comment clarifying crypto.Hash(0)
* Update ed25519.go
Co-authored-by: Christian Banse <oxisto@aybaze.com>
Oleksandr Redko