D-bot stepper mounts with zip tie slots

The PETG-printed mount plates on the stepper motor mounts for my D-bot would flex a little when the steppers are under belt tension, leading to the stepper being bent over a little bit so their drive shafts weren't perfectly vertical anymore. It wasn't a huge deal, but even a little angle in the stepper drive shaft toward the printer can cause the belt to bunch up on one end of the drive pulley.

I remixed this in Tinkercad by simply adding two slots (left side mount) and one slot (right side