[Docs]: Select widget - Server side Filtering

[Nikhil-Nandagopal]

Add the sample app and elaborate on the same use case.

[danciaclara]

Looks like we have added this section already - https://docs.appsmith.com/reference/widgets/dropdown-1#server-side-filtering

We can also link the Sample App @jnikhila @Pranay105

[spark-c]

Asked pranav about status of the sample app since it was a bit confusing without instructions for users

[danciaclara]

@spark-c You can add the steps from the video that is on this page. We can add the sample app later on as well

[spark-c]

PR In review here