chore: update BLS aggregate signature example

Author: b00f

examples/example_bls_multisig.py

@@ -0,0 +1,28 @@
+from pactus.crypto.bls.private_key import PrivateKey
+from pactus.crypto.bls.public_key import PublicKey
+from pactus.crypto.bls.signature import Signature
+
+
+def main() -> None:
+    msg = "some message".encode()
+    prv1 = PrivateKey.random()
+    prv2 = PrivateKey.random()
+
+    pub1 = prv1.public_key()
+    pub2 = prv2.public_key()
+
+    sig1 = prv1.sign(msg)
+    sig2 = prv2.sign(msg)
+
+    agg_pub = PublicKey.aggregate([pub1, pub2])
+    agg_sig = Signature.aggregate([sig1, sig2])
+
+    if not agg_pub.verify(msg, agg_sig):
+        print("Signature verification failed")
+        exit(1)
+
+    print(f"Aggregated signature: {agg_sig.string()}")
+
+
+if __name__ == "__main__":
+    main()