fix the readme for using firebase db example

Author: nisrulz

using_firebase_db/README.md

@@ -1,6 +1,13 @@
-# using_firebase_db
+# Using Firebase DB
 
-A very basic note taking app to demonstrate the usage of firebase realtime database with flutter. Follow this [guide](https://firebase.google.com/docs/flutter/setup) to setup firebase to work with flutter. This demo will not work without the `google-services.json` file. Add notes by using the Floating Action Button and delete notes by long pressing them.
+A very basic note taking app to demonstrate the usage of firebase realtime database with flutter. Follow this [guide](https://firebase.google.com/docs/flutter/setup) to setup firebase to work with flutter.
+
+Add notes by using the Floating Action Button and delete notes by long pressing them.
+
+>This demo will not work without the `google-services.json` file. 
+
+
+<img src="demo_img.jpg" height="600em" />
 
 ## Getting Started