Add CAD-to-URDF (OnShape) simulation wiki entry (#244)

Adds a new simulation wiki guide covering an end-to-end CAD-to-URDF workflow using OnShape, including:

- CAD import options (native SolidWorks vs STEP)
- Link naming and mate/joint setup
- Joint limits and export steps
- URDF validation and common troubleshooting
- Isaac Sim import notes

Author: kodikarthik21

_data/navigation.yml

@@ -262,6 +262,8 @@ wiki:
         url: /wiki/simulation/an-introduction-to-isaac-sim/
       - title: Simulating UGVs in Unity
         url: /wiki/simulation/simulating-ugvs-in-unity/
+      - title: Creating a URDF from a CAD Model using OnShape
+        url: /wiki/simulation/cad-to-urdf/
   - title: Interfacing
     url: /wiki/interfacing/
     children:
@@ -409,4 +411,4 @@ docs:
   - title: Contribute
     children:
       - title: Introduction
-        url: /docs/
+        url: /docs/

assets/images/simulation/export.png

@@ -30,6 +30,9 @@ This section focuses on **simulation tools, techniques, and environments** for r
 - **[Spawning and Controlling Vehicles in CARLA](/wiki/simulation/spawning-and-controlling-vehicles-in-carla/)**
   A hands-on tutorial for spawning and controlling vehicles in the CARLA simulator. Covers connecting to the CARLA server, visualizing waypoints, spawning vehicles, and using PID controllers for motion control. Demonstrates waypoint tracking with visual aids and includes example scripts for quick implementation.
 
+- **[Creating a URDF from a CAD Model using OnShape](/wiki/simulation/cad-to-urdf/)**
+ Step-by-step instructions for generating URDFs from OnShape. Includes best practices for assembly cleanup in SolidWorks, defining revolute and prismatic joints, and fixing common mesh and coordinate transform errors.
+
 ## Resources
 
 ### General Simulation Tools