Add collision handlers tutorial

[viblo-majority]

Summary

• Add a new documentation tutorial explaining how collision handlers work in Pymunk
• Covers all four callback phases: begin, pre_solve, post_solve, and separate
• Includes practical examples like one-way platforms and brick-breaking mechanics

Details

The tutorial is aimed at users who have completed the basic SlideAndPinJoint tutorial and want to learn more advanced collision handling techniques. It covers:

• Understanding the four collision callback phases
• Setting up collision types
• Registering collision handlers with space.on_collision()
• Using begin callback to control collision processing (one-way platforms)
• Passing custom data to handlers (game state, score tracking)
• Using post_solve to read collision impulses for impact effects
• Modifying collision properties in pre_solve
• Wildcard collision handlers
• A complete working example demonstrating all concepts