Support creating a Schnorr Signature given a message

[cjackie]

I'm working a nostr client in Python, and Nostr uses Bitcoin Schnorr signature for signing. It would be great that python-bitcoinlib would support that, and since the signature is support since TAPROOT, it should be in the library.

Thanks

[timqi]

Use btclib https://github.com/btclib-org/btclib instead