Drop-in t-slot nuts for 8mm slots (30mm profile)

I needed some drop in nuts for 30mm aluminum extrusion profile and found the original from #whosawhatsis with the Open Scad source. So I modified a bit to fit my profiles.

It is still for M3 nuts and bolts but I rotated the nut and bolt hole 30 degree to allow for a better overhanging prints.

Also, I added a slot to allow the nuts to be turned with a flat-head screwdriver.