Anet A6 power supply cover with side switch

**UPDATE**: Though this cover prints quickly and does it job, it lacks proper fixation to the frame and will move around. I've made a much more solid and robust cover; check it out [over here](https://www.thingiverse.com/thing:2851854).

This is yet another cover for the Anet A6 that has a hole for a switch. It's basically traced from [TodayAtTheCanteen's design](https://www.thingiverse.com/thing:2001954), but I couldn't edit that one in FreeCad without errors, so I remade it.

It's sized fo