Backback hanger/hook

It's a hook that's the same size as a typical clothes hanger. Overbuilt so that it can hold a loaded backpack.

**Update 2022-12-01:** Version 1 broke after two months. Version 2 was redesigned to be stronger (64 mm² cross section).

**Update 2024-08-07:** Version 2 broke after a little under two years hanging a 7 kg load. Version 3 was redesigned to be stronger (145 mm² cross section).