Update README: clarify Java 11 support and setup instructions

[anushkax2311]

Summary

This PR updates the README to improve clarity and correctness for new users.

Changes

• Clarified that Java 11 is the recommended version
• Improved project structure documentation
• Aligned installation, build, and test instructions
• Improved Markdown formatting for readability

Motivation

The previous README contained outdated Java version information and unclear setup instructions, which could cause confusion during compilation and testing.

[cyrille-artho]

Hi,
Thank you for your PR. I am able to compile your code and run the "test" build target, but no unit tests are run. I will look more into this.
Your PR did not affect the unit tests, so the unit tests not running has a different reason.