[Feature Request] Improve Hybrid A* with Reeds-Shepp Paths and Reversing Support #49

Description
Currently, the existing sample code of Hybrid A* Path Planning doesn't support reversing movement.
To make it more practical and professional -- similar to those used in autonomous valet parking -- we need to upgrade the heuristic and the motion model.

I would like to propose an enhancement to the Hybrid A* algorithm by integrating the Reeds-Shepp curves.

Tasks

• Integration of Reeds-Shepp Paths: Use Reeds-Shepp curves as the analytic expansion (shot-to-goal) to improve search efficiency and path quality.
• Support for Reversing: Update the motion model to allow the vehicle to move to backward.
• Direction Change Penalty: Implement a cost function that penalizes switching between forward and backward to ensure smooth paths.
• Heuristic Update: Improve the heuristic considering the non-holonomic constraints.

Reference Code
Current version of Hybrid A* Global Path Planning