Re-export multihash & multiaddr types (#79)

This is a companion PR to
paritytech/polkadot-sdk#4198.

src/crypto/ed25519.rs

@@ -202,6 +202,11 @@ impl SecretKey {
         sk_bytes.zeroize();
         Ok(SecretKey(secret))
     }
+
+    /// Convert this secret key to a byte array.
+    pub fn to_bytes(&self) -> [u8; 32] {
+        self.0.to_bytes()
+    }
 }
 
 #[cfg(test)]

src/types.rs

@@ -22,6 +22,14 @@
 
 use rand::Rng;
 
+// Re-export the types used in public interfaces.
+pub mod multiaddr {
+    pub use multiaddr::{Error, Iter, Multiaddr, Onion3Addr, Protocol};
+}
+pub mod multihash {
+    pub use multihash::{Code, Error, Multihash, MultihashDigest};
+}
+
 pub mod protocol;
 
 /// Substream ID.