enable or disable the saved event of Observer

[danielhuang-030]

Hi, thank you for developing this package, it is great!
But there is a suggestion for use.
Because the models will always trigger the saved event and then add the queue when save.
However, sometimes updated data may not be related to index.
Hope that new parameters can be added to the config to enable/disable the saved event of Observer.
Let us decide when we want to add a queue.

Thanks again.