Pi ZeroW case with screws and CS mount

Slight remix of bobtidey's excellent design (I love the camera cable slot and the fact its OpenSCAD!)

I've basically changed it to take m2.5 (id) x 3.5 (od) x 4mm long [knurled inserts](https://www.aliexpress.com/item/UXCELL-M2-5-X-4Mm-3-5Mm-Od-Brass-Threaded-Insert-Embedded-Knurled-Thumb-Nut-100Pcs/32776245817.html), made it slightly taller, removed the screw countersink (as I plan on using [allen hex heads](https://www.aliexpress.com/item/304-Stainless-Allen-Bolt-Socket-Cap-Screw-Hex-Head-A