title: How to get Firestore RecyclerView items' document id when click
body: <p>I have followed the answer to a question well on the link below on how to create Firestore RecyclerView with database, <a href="https://stackoverflow.com/questions/49277797/how-to-display-data-from-firestore-in-a-recyclerview-with-android#">How to display data from Firestore in a RecyclerView with Android?</a> 
  Now I want to get the items position (I mean document id) of the recyclerView items, I need it in an intent so that I can reference to the particular document in my collections. (In the new activity)</p>