Introduce Feature First Structure for Enhanced Modularity

[Erengun]

This PR introduces the Feature First structure to the Flutter Riverpod 2.0 template, enhancing the modularity and maintainability of the codebase. The Feature First approach organizes code into self-contained features, each with its own set of responsibilities and dependencies, leading to a more intuitive and scalable project structure.

Changes:

• Restructured the lib directory to follow the Feature First approach.
• Moved feature-specific code from lib to dedicated feature directories under lib/features.
• Created common, config, constants, data, di, exceptions, localization, routing, and utils directories within lib to hold shared resources and utilities.

Benefits:

• Modularity: Each feature is now self-contained, making it easier to understand, develop, and test.
• Scalability: The structure supports the addition of new features without introducing unnecessary complexity.
• Maintainability: Shared resources are centralized, reducing duplication and making it easier to update dependencies across features.

Example of Feature Directory Structure:

Hey i have a flutter riverpod 2.0 template in github write me a short pr content that introduces feature first structure

‣ lib ‣ common ‣ config ‣ constants ‣ data ‣ di ‣ exceptions ‣ features ‣ home ‣ info ‣ ... ‣ localization ‣ routing ‣ utils

**Next Steps:**

- Ensure that existing features are refactored to align with the new structure.
- Update documentation to reflect the new organization.
- Review the current CI/CD pipeline to ensure it accommodates the new structure.

**Testing:**

- Manual testing of the application has been performed to confirm that all features function as expected.