DIY 3D Mouse

This is my take on a DIY spacemouse project, inspired by https://www.instructables.com/DIY-Space-Mouse-for-Fusion-360-Using-Magnets/ My main change is in the firmware core (available at https://github.com/wiz78/3DMouse), which makes it a standard USB HID device, compatible with 3Dconnexion's driver, thus making it more flexible than a device which simply sends hard-coded keyboard shortcuts. I didn't like the idea of pausing the print to put BB's in it, so I made room for tyre balanci