Customizable squares for one-layer bed leveling test

This is a set of simple square single-layer chips for testing bed levelling.

The customizable OpenSCAD file allows setting the size of the sides, the gap between chips, the thickness, and the repetitions on a grid.

Per the instructions at https://www.thingiverse.com/thing:3685657
and https://www.matterhackers.com/articles/3d-printing-essentials-first-layer you can use this to diagnose your first layer height.

A single 20x20x0.2mm chip should take about 2 minutes to print, and a plate of 9 would take correspondingly longer.


Try to get your printer to print a single-layer chip with accurate dimensions and quality by adjusting your bed leveling, Z-offset, first layer settings, extrusion multiplier, etc....



The OpenSCAD code basically wraps the [cube()](https://en.wikibooks.org/wiki/OpenSCAD_User_Manual/Primitive_Solids#cube) module in a nested for loop:

````

module mesh_of_squares(){
for (i = [0:reps-1]){
translate([(side_mm+gap_mm) * i, 0, 0])
for (j = [0: