Can we have AsyncVerifier please

[Gozala]

Can we please get AsyncVerifier as dual for AsyncSigner

traits/signature/src/signer.rs

Lines 227 to 238 in 6a95ecc

	/// Asynchronously sign the provided message bytestring using `Self`
	/// (e.g. client for a Cloud KMS or HSM), returning a digital signature.
	///
	/// This trait is an async equivalent of the [`Signer`] trait.
	pub trait AsyncSigner<S> {
	/// Attempt to sign the given message, returning a digital signature on
	/// success, or an error if something went wrong.
	///
	/// The main intended use case for signing errors is when communicating
	/// with external signers, e.g. cloud KMS, HSMs, or other hardware tokens.
	async fn sign_async(&self, msg: &[u8]) -> Result<S, Error>;
	}

Rationale: Web crypto APIs do not support sync verification so any code that target it needs to come up with own traits to deal with the gap.

[tarcieri]

That seems reasonable enough