Add white-box unit tests for collision modules

[Manahil-Afzal]

This PR is attempting to solve following
Issue #352

WHAT I Have Done
-> Added complete white-box unit tests for the collision system.
-> Covered all main modules: Brute, QuadTree, and utils.
-> Ensured each module is tested under different collision scenarios.
-> Followed the required folder structure for the collision tests.

WHY I Did This
-> Collision detection is a core part of Music Blocks v4.
-> Tests ensure correctness, stability, and predictable behavior.
-> Helps avoid regressions in future updates.
-> Supports future contributors with a reliable foundation.

Summary of Changes:

Added tests for Brute.ts:
• Overlapping object detection
• Non-overlapping object detection

Added tests for QuadTree.ts:
• Object insertion
• Collision detection within regions

Added tests for utils/index.ts:
• Rectangle–rectangle collision
• Circle–circle collision

Organized files as follows:
📦collision
┣ 📂spec
┃ ┣ 📜Brute.spec.ts
┃ ┣ 📜index.spec.ts
┃ ┗ 📜QuadTree.spec.ts
┣ 📂utils
┃ ┗ 📜index.ts
┣ 📜Brute.ts
┣ 📜index.ts
┗ 📜QuadTree.ts

Please let me know if any improvements or additional test cases are required.
Thank you!