Add a verify function to PublicKey

Expose signature verification functionality for schnorr signatures on
the `XOnlyPublicKey` type.

src/key.rs

@@ -1316,6 +1316,16 @@ impl XOnlyPublicKey {
     pub fn public_key(&self, parity: Parity) -> PublicKey {
         PublicKey::from_x_only_public_key(*self, parity)
     }
+
+    /// Checks that `sig` is a valid schnorr signature for `msg` using this public key.
+    pub fn verify<C: Verification>(
+        &self,
+        secp: &Secp256k1<C>,
+        msg: &Message,
+        sig: &schnorr::Signature,
+    ) -> Result<(), Error> {
+        secp.verify_schnorr(sig, msg, self)
+    }
 }
 
 /// Represents the parity passed between FFI function calls.