Simple customizable flexible chain ear-saver

I admired the [Flexi-Turtle Ear Saver](https://www.thingiverse.com/thing:4293567) but found that all the decorative details got caught in my hair. The idea seemed a great one, though --- making a one-piece chain to mimic flexibility in a stiff material like PLA or ABS, and I resolved to make a less decorative design which served the same purpose. So this design is a pretty simple length of chain, with horns sticking out of one side (the outside, as you put it on your head), to loop a mask around.

OpenSCAD source is included, and most of the relevant parameters are named and configurable, so you can make your chain longer, thicker, or looser, and can make the quills appear only on some chains, or longer, or wider. Tilting the horns further than the default _may_ cause support issues, since eventually there'll be too much overhang to print cleanly.

UPDATE (08 FEB 2021): I added a "tweak factor" to make the nesting a little looser at the bottom, which should allow for (a) easier bre