how to integrate jquery select2 plugin as dropdown in AEM forms as custom apperance field, but cannot find any document or complete working example

[DavidZhang]

How to integrate with the data binding? Seems Adobe AEM and Forms site has no many spelling errors causing almost 90% of the example code on the web site is not working by default, is this on purpose?

Look at this example, 

Create custom appearances for adaptive form fields | Adobe Experience Manager

There's no code to download and runnable.