Add edit delete user - Using Provider

[adityazanzane-coditas]

Implement Provider for User Management

Description

Implemented Provider for managing user data throughout the application.

Screenshot

PR Checklist

• Build success
• Tested

Updates

• Changed setState to Provider and implemented ChangeNotifierProvider for state management.
• Added a new file 'user_provider.dart' containing User Provider with Dummy List and functions like add, update, and delete.
• Updated User List Screen and User Edit Screen UI using Card Widget for better visualization.
• Improved UI design in both screens with creative elements.
• Custom validation methods added in User Edit Screen for form validation instead of using form widget.
• Implemented an alert dialog box for confirmation when removing a user from the list.