BIQU Thunder Adjustable Z-axis Endstop

I wanted an adjustable Z-axis endstop for my BIQU Thunder to allow me to use a PEI coated spring steel bed surface with both the mechanical endstop and the included auto-level sensor. This was based on a [CR-10 endstop](https://www.thingiverse.com/thing:2727769) by [sfandersen](https://www.thingiverse.com/sfandersen/) but redesigned to fit the BIQU Thunder.

You'll need:
1 - M4 Nyloc nut
1 - M4 bolt ~30mm long