Adding water mode to physics game

[HarleenKaurBhullar]

I have added a Water Mode to the physics game by creating a custom environment using the PhysicsJS library, It resoves #1863 Since PhysicsJS does not provide an inbuilt water or fluid module, I implemented a custom solution based on the concepts of buoyancy and drag force to simulate objects sinking and floating in water.

This pull request includes:

• A custom environment for water physics
• Implementation of buoyant force and drag to approximate fluid behavior
• Visual demonstration of objects floating and sinking based on their properties

I have attached a short video demonstrating the current behavior and implementation. If this aligns with the project goals, I’d be happy for this to be merged. I would really appreciate it if you could take a look and share your feedback or suggestions for improvement. Any reviews are welcome!

Screencast from 2026-01-02 17-48-32.webm