message: docs: add description for app
diff: @@ -41,6 +41,8 @@ const client = new KintoneRestAPIClient();
  - All methods are defined on the `app` property.
  - This method returns a Promise object that is resolved with an object having properties in each `Returns` section.
  +- All methods that start with `add`/`update`/`delete` are applied to pre-live settings.<br />
  + Use [`deployApp()`](#deployApp) to deploy the pre-live settings to the live app.
  ## Methods
  