message: Add template description for action creator
diff: @@ -785,6 +785,9 @@ export default class BaseServer<
  /**
  * @param actionCreator Action creator function.
  * @param callbacks Callbacks for action created by creator.
  + *
  + * @template AC Action creator function.
  + * @template D Type for `ctx.data`.
  */
  type<AC extends ActionCreator, D extends object = {}> (
  actionCreator: AC,
  