[HD-WALLET] add one example

rfc/0015_Dubp_HD_Wallet.md

@@ -51,3 +51,16 @@ So, the ith outward payment is made on the `m/a'/0'/i` keypair, where `a` is the
 
 [Dubp-Mnemonic]: https://git.duniter.org/documents/rfcs/blob/dubp-mnemonic/rfc/0014_Dubp_Mnemonic.md
 [BIP-Ed25519]: https://drive.google.com/file/d/0ByMtMw2hul0EMFJuNnZORDR2NDA/view
+
+### Examples
+
+#### Example 1
+
+mnemonic: `"acquire flat utility climb filter device liberty beyond matrix satisfy metal essence"`  
+seed: `0x4643ecce02b307e3eacd6c838c520c2768882e5e4f1877121b443c5f14c16848`  
+account_id: `2`
+
+External public key (path `m/2'/0'`): `HWy7CLMNJCvk7QYYax5xxbLoqDqMj9fv5DSnfLcmpjEe`
+external chaincode: `EQt2iaLkHD9BArGwp2daFxrCNCDBC76AwErg7HmGgSBq`
+
+Third external address (path `m/2'/0'/3`): `BuerND7fRF1DWV8KxYftmwQ3gLWenPE3TGeb3cJnWNAd`