Add init optional method to Keyring type (#99)

Author: gantunesr

src/keyring.ts

@@ -81,6 +81,11 @@ export type Keyring<State extends Json> = {
    */
   deserialize(state: State): Promise<void>;
 
+  /**
+   * Method to include asynchronous configuration.
+   */
+  init?(): Promise<void>;
+
   /**
    * Remove an account from the keyring.
    *