M3 screw knob (parametric)

I designed this for [the knurled M3 screws I got on Amazon](https://www.amazon.com/gp/product/B0714FLXND/ref=ppx_yo_dt_b_asin_title_o08__o00_s00). I'm using these with [embedded M3 nuts](https://www.amazon.com/gp/product/B01IYWTCWW/) and [some multiwave washers](https://www.amazon.com/gp/product/B07B45Y37D/) to add the legs and feet from [MichaelTV's Iris case](https://www.thingiverse.com/thing:3392322) to [AGuyFromOhio's Ergodox case](https://www.thingiverse.com/thing:2533064). You can use the Customizer app to adjust the knob and socket sizes, and knurling, to fit your needs, or you can edit the included OpenSCAD file directly.

My goal was to make something big enough to be useful but small enough to not get in the way or add significant bulk to the case build. The screw head sockets are shallow enough that the knob stops maybe a tenth of a millimeter or so short of the screw head's bottom lip, which helps ensure the knobs don't end up rubbing against the tent legs.

The socket