Draft: Implement new electronics defaults

Since the discussion at design review in June last year, the electronics situation has changed significantly. Crucially, Sangaboard v5 is available via taulab.eu thanks to Filip. He is also selling an illumination board that works with the programmable constant-current source on the Sangaboard.

I think it makes sense to adopt Sangaboard v5 and the associated illumination board as the default electronics option. The work-around using a Nano (or Pi Pico) and 5mm LED is probably the best fall-back option. It does no harm to mention previous Sangaboard versions, but we should discourage anyone from using them, as they're likely to get confused and the v5 is significantly better than any of the previous options.

This will require a number of changes to the instructions, specifically:

• Update the illumination assembly renders
• Check the illumination assembly page
• Amend the electronics page
• Amend the sangaboard and sangaboard v5 part pages
• Amend the illumination PCB page

A more detailed list of actions is given in the OFEP.

Closes #307