[chore] Update README with project specifications and goals

[pedrobiqua]

The current README is minimal and does not explain the project clearly. Update it to include:

• Project objectives and motivation (why this project exists).
• Description of the main algorithms and structures to be implemented (e.g., KDTree, BallTree, etc.).
• Explanation of the learning purpose behind the implementations.
• Basic usage instructions and examples.

This will help new contributors and users to quickly understand the scope and purpose of the project.