code improvement and dependencies update

Author: ankesh-kumar

README.md

@@ -2,8 +2,8 @@
 A Chat Helper for create chat application in Flutter using Firebase as backend services.
 
 
-# Checkout Androia app Demo
-[<img src="https://1.bp.blogspot.com/-wBzKHsSOXqo/YNBgNi4nGtI/AAAAAAAAQBc/8CNU9jwS9s8MxykqmkxyD1QOY7FnI_OdwCLcBGAsYHQ/s320/play_store_image.png" width="250px" height="150"/>](https://play.google.com/store/apps/details?id=com.smartmobilevilla.just_chat)
+# Checkout Android app Demo
+[<img src="https://1.bp.blogspot.com/-wBzKHsSOXqo/YNBgNi4nGtI/AAAAAAAAQBc/8CNU9jwS9s8MxykqmkxyD1QOY7FnI_OdwCLcBGAsYHQ/s320/play_store_image.png" width="350px" height="150"/>](https://play.google.com/store/apps/details?id=com.smartmobilevilla.just_chat)
 
 # Checkout Web Demo
 [Just Chat Web Demo](http://justchat.smartmobilevilla.com)