Wire Harness: Pinch Valve

[inceptionev]

Create the pinch valve stepper motor harness design and its associated assembly documentation.

• Origin: PCB J38 and J49 Molex Micro-Fit 3.0 1x4
• Destination: Stepper Motor on the pinch valve
• Wire recommendation: use the wire already attached to the stepper motor, just cut off the manufacturer-supplied connector.
• Length: 300mm (conservative estimate; may be refined in integration)
• Pinout references: ventilator PCB schematic, this image:

A tutorial is available in our wiki here: https://github.com/RespiraWorks/Ventilator/wiki/Designing-Wire-Harnesses-with-WireViz

• [x] Create a branch for the new harness
• [x] Add components to the json library at: master/docs/purchasing/parts.json
• [x] Create the harness source file using WireViz
• [x] Run WireViz to check your work
• [x] Create a documentation page for the harness in reStructured text
• [x] Commit only the .yml and .rst files, and any images you references in the harness source file.
• [ ] Create a pull request for the harness branch