Duckiebot upgrade kit: DB21M or DB21J to DB21J-v3

This chassis upgrade kit contains components that bring your DB21 (M or J) up to DB21J-v3 specifications. 

Advantages over the DB21-J model include: 

• New omnidirectional wheel offering several improvements over the previous model:
  
  
  • uniform rolling friction in all directions;
    
    
  • three points of contact with the chassis (instead of two) for enhanced rigidity and smoother rides;
    
    
  • Serviceability: this wheel can be easily opened and cleaned up of dust and fibers collected through extended use, increasing the lifespan of the robot.
    
    
• Updated chassis: design improvements on the chassis, introducing compatibility with:
  
  
  • the new omnidirectional wheel;
    
    
  • more NVIDIA Jetson Nano boards: including the NVIDIA Jetson Nano Super Orin developer kits and different versions of the NVIDIA Jetson Nano 4GB developer kits, e.g., Waveshare's and RS Components C-100 models.
    
    
• Improved chassis lock-in mechanism: a set of Nylon screws and nuts with improved mechanical tolerances reduces Duckiebot assembly time (and stress) by at least 10%.