Improved README with Detailed Project Overview and Documentation Links

This update enhances the README file by providing a clearer and more structured overview of the MariaDB Server project.

Changes Made:

Improved overall project description

Added clear explanation of MariaDB and its purpose

Organized documentation and resource links

Updated build and contribution instructions section

Improved formatting for better readability

Purpose:

The goal of this update is to make the README more informative and beginner-friendly, helping contributors and users better understand the project structure, documentation resources, and contribution process.