GBB15 CAN bus stepper board for 1515 extrusions

A gantry-mounted CAN stepper driver board for 15mm aluminum beams (mostly for PrintersForAnts printers). This board can be used e.g. for the Micron to have A/B motor controllers directly at the gantry. This reduces the number of wires required to be routed to the gantry. Additionally, this board can be used for Voron-0 or Tridents as a USB to CAN converter (using the Klipper CAN bridge option) with included A/B motor controllers. PLEASE NOTE: If you are going to use the CAN output to run an umbilical to your CAN toolhead board you need to remove the “120 R” surface mount resistor (and add a 120 ohm terminating resistor at the toolhead). More info can be found here:  GBB15