Robot car kit additions: U.S. mount, standoffs, and bumpers

These things are designed with Tinkercad. Edit them online:
- U.S. mount and standoffs: https://www.tinkercad.com/things/4pYk4dzTUIs
- Front bumper: https://www.tinkercad.com/things/j7IARV6cSri
- Back bumper: https://www.tinkercad.com/things/kUJ1W0sJkmt
- Circuit for sensing is also shown as tinkercad circuit project: https://www.tinkercad.com/things/jznavQ265LV
The Robot kit from Banggood is missing some parts. These are complementary parts. - U.S. mount is for helping to attach the US sen