Generic webcam mount for Ender 3

I redesigned the mount to support any generic webcam with a width between ~35 mm and ~60 mm. Lower than 35 mm should also work, but will probably not be as stable.

The middle part of the mount (grip_middle) has a fairly long bridge, but it's doable without supports.

I've split the clamp from the arm and added a connector. This allows printing without supports. It's a tight fit so it's pretty stable, but you can glue these parts to make sure.