Box rack for AliExpress boxes

[ Update: April 11th, 2021 ] Added feet for the extrusion, to be printed in TPU/TPE :)

## This is a storage rack for those boxes you get your screws, connectors etc. in from China. I have accumulated about 20 of these boxes and they need a home.

### UPDATE1:
- Extrusion cap tolerance verified; fits perfectly.
- Peg strength failed. Tolerance is ok, but removing the supports broke the piece. Redesign in progress.

### UPDATE2:
- Pegs redesigned, sturdier, 90 degrees, so universal for both sides. Boxes will now not be fully horizontal, but that should not be a real problem.
- Also corrected a few numbers in the parts list.

### UPDATE3:
- I ordered extrusions for a double rack, expect them delivered in 2 weeks, will build a rack and post pictures :)

### UPDATE4:
- finally added the appropriate attribution
- updated the text to reflect the progress of the design
- currently printing and testing new end-cap design (the part that goes into the extrusion, that is. The vi