adding a filter in the search text listener to emit after typing 3 characters

[mootazltaief]

adding a filter in the search text listener example witch start searching only after typing at least 3 characters

[kaushikgopal]

@mootazltaief thanks for the contribution.

Only problem is i feel that adding more conditions would complicate the example and move away from the original intent. I think we're using the .filter in the retrofit example if peeps want to understand the usage of the .filter operator.

Cheers.