title: Angularfire; how to add new data into existing firebase list object
body: <p>Suppose i have Firebase there is list of object called firebaseList having an object KF6dlZnUlilVtNykDEN with one property title : "value" and i want to add an array in this existing KF6dlZnUlilVtNykDEN how can i do that?</p>
  
  <p>Actually i want to build Facebook like firebase, post and their comment suppose if title is post so how to structure for comment data</p>