Add more tolerance to cavity_top_allowance (#124)

I think the default should add a bit more tolerance to the hight of the cavity. I just printed it and it's about 3 cards too low for me. Perhaps the vinyl added unexpected thickness. I think 3mm extra should be good.

Author: lastcoolnameleft

3d/tools/flap_container.scad

@@ -21,7 +21,7 @@ num_flaps = 40;
 containers_x = 1;
 containers_y = 1;
 
-flap_thickness_allowance = 1 - flap_thickness;  // fudged, so all flaps are considered 1 mm thick
+flap_thickness_allowance = 1.1 - flap_thickness;  // fudged, so all flaps are considered 1.1 mm thick
 cavity_top_allowance = 2;  // extra case height above the flaps
 
 flap_clearance = 0.5;  // distance between the flap edges and the case walls