Update README.md

Refactored the image loading for postcard Profile image

Saving fcm token to firebase

Fixed navigation for login & signup screens.

Added Caching for Profile Screen & PostCard Profile icon,

Verifying user email on signing up, Fixed null value bug

Handled no data for comments on comment screen

Add firebase_notifications package,

Organized imports and added firebase_messaging package

Fixed overflow on the profile screen

Added a loading bar to posts and implmented caching for posts.

Updated project description in pubspec.yaml for first release of app.

Fixed empty field submission bug,

Added flutter_launcher_icon package & app icon

Fixed Overflow issues for signup screen