bring back `setUsername` that was removed by mistake

index.js

@@ -203,6 +203,19 @@ export function setGenericPassword(
   );
 }
 
+/**		
+  * Saves the `username` for further use on get requests.		
+  * @param {string} username Associated username or e-mail to be saved.		
+  * @return {Promise} Resolves to `true` when successful		
+  */		
+export function setUsername(		
+  username: string		
+): Promise {		
+  return RNKeychainManager.setUsername(		
+    username
+  );
+}     
+
 /**
  * Fetches login combination for `service`.
  * @param {string|object} serviceOrOptions Reverse domain name qualifier for the service, defaults to `bundleId` or an options object.