Lack Pi Camera Arm (Corner Mount)

I wanted to mount my Pi Camera to one of the Lack legs, but I didn't want to remake one of the spacers. I decided to fix the camera to the inside corner.

The ball-joint is 12.5mm in diameter, so it works great with a camera housing like the one in [hackoholic](https://www.thingiverse.com/hackoholic/about)'s camera mount. It can be [found here](https://www.thingiverse.com/thing:2352964).