Ed25519 Private Key
The getEd25519PrivateKey method returns the user's Ed25519 private key.
Use this key to sign transactions on Solana, Near, Algorand, and other chains that use the Ed25519
curve.
This method throws an error if no user session exists or if the key is unavailable.
Usage
let ed25519PrivateKey = try web3Auth.getEd25519PrivateKey()