Add USB Support from my Fork

[SartorialGrunt0]

Hello,

The current release of STL's doesn't support a USB input with a cover installed. In my fork I have added a 2020, 1515 extrusion mount, added a hole for the USB port in part [a]_cover, and modified the wire_cover.stl to remove the JST. Do you want to merge this into your main? I have tested it and everything seems to fit well, but a second tester wouldnt be bad.

[EricZimmerman]

@SartorialGrunt0 can you elaborate with a photo how your 1515/2020 mounts work? which bolt does it attach to?

[SartorialGrunt0]

@SartorialGrunt0 can you elaborate with a photo how your 1515/2020 mounts work? which bolt does it attach to?

My fork has the step and STL files. I also have the CAD models in Onshape if it's helpful.