Add methods for getting xPub of root node and getting private key for…

… an address

src/wallet/hdwallet.ts

@@ -85,6 +85,15 @@ export abstract class AbstractHDWallet {
         return (this.constructor as typeof AbstractHDWallet)._coinType!;
     }
 
+    /**
+     * Returns the extended public key of the root node of the HD wallet.
+     *
+     * @returns {string} The extended public key.
+     */
+    get xPub(): string {
+        return this._root.extendedKey;
+    }
+
     /**
      * Derives the next valid address node for a specified account, starting index, and zone. The method ensures the
      * derived address belongs to the correct shard and ledger, as defined by the Quai blockchain specifications.
@@ -223,6 +232,18 @@ export abstract class AbstractHDWallet {
         return addressInfo;
     }
 
+    /**
+     * Returns the private key for a given address. This method should be used with caution as it exposes the private
+     * key to the user.
+     *
+     * @param {string} address - The address associated with the desired private key.
+     * @returns {string} The private key.
+     */
+    public getPrivateKey(address: string): string {
+        const hdNode = this._getHDNodeForAddress(address);
+        return hdNode.privateKey;
+    }
+
     /**
      * Gets the addresses for a given account.
      *