docs: Enhance Tech Stack section in README

This commit updates the `README.md` to provide a more detailed and structured "Tech Stack & Key Libraries" section.

Key changes:
- Replaced the simple "Built With" list with a more comprehensive "Tech Stack & Key Libraries" section.
- Categorized libraries into UI Toolkit, Architecture & Navigation, Data Handling, and Build & Development Tools.
- Added specific libraries like Material 3 Expressive Components, Material Icons Extended, Hilt, Jetpack Navigation 3, Kotlinx Serialization, Spotless, and KtLint.
- Included links to the respective library documentation or project pages.