Add PICO-8!

[blockhole72]

Maybe add some variants of sound chips, like Sunplus' clone of the Yamaha MA-2.

[tildearrow]

PICO-8 is not possible:

• It only provides very limited options to control sound "registers" (in quotes because most of these are fake)
• It's more of a digital synthesizer than a retro sound chip
• It's closed source (there's a GPL-licensed reimplementation, but sadly it's under GPLv3 so no good for Furnace)
• It wouldn't make much sense to add anyway since PICO-8 already has a built-in music editor