ed25519PkToCurve25519 was calling libsodium sk_to_curve in both native and jvm platforms. Fixed so it calls appropriate pk_to_curve. Fixes #20

multiplatform-crypto-libsodium-bindings/src/nativeMain/kotlin/com/ionspin/kotlin/crypto/signature/Signature.kt

@@ -207,7 +207,7 @@ actual object Signature {
         val x25519PublicKey = UByteArray(crypto_scalarmult_curve25519_BYTES)
         val x25519PublicKeyPinned = x25519PublicKey.pin()
         val ed25519PublicKeyPinned = ed25519PublicKey.pin()
-        crypto_sign_ed25519_sk_to_curve25519(
+        crypto_sign_ed25519_pk_to_curve25519(
             x25519PublicKeyPinned.toPtr(),
             ed25519PublicKeyPinned.toPtr()
         )
@@ -272,4 +272,4 @@ actual object Signature {
         return publicKey
     }
 
-}
+}