Optimized Adjustable Band for Face Shield

Simple design of an adjustable band for a face shield. These are printed vertically to increase speed and serrated to allow better hold. Not infinitely reusable, but they are quite strong and flexible.

Original design by *gnome053* here: https://www.prusaprinters.org/prints/28515-face-shield-adjustable-head-band/comments

Optimized for printing with 0.4mm nozzle and 0.45mm line width, but 0.8mm nozzle and 0.9mm line width should probably work as well.