Customizable Tslot profile with nubs

This is a remix of kijja's https://www.thingiverse.com/thing:4192506

I added some comments to the corner bracket module to help me learn what was going on, then added optional alignment nubs to the vertical face. It's a soft overhang and prints fine on a Creality Ender 3 Pro and should work on most printers fine. The nubs are useful to help keep parts from rotating should they not be tight enough as well as helps with assembly. They can be easily turned off and if so, there should be no changes from kijja's fine original work.

More of kijja's work:

Compatible with T-slot side cover
https://www.thingiverse.com/thing:4218924

Other V-slot profile
https://www.thingiverse.com/thing:4257839

Kijja's profile:
https://www.thingiverse.com/kijja/designs