[F.Rq.] SNES rumble

This is a homebrew standard. spec

Since it's over the controller ports, I thought we might be able to implement it by snooping on the controller registers with a hook (since at least new BSNES implements them), but my test was fruitless:

local buffer = {};
event.on_bus_write(function(addr, val, flags)
	table.insert(buffer, bizstring.hex(val));
end, 0x4016);
while true do
	emu.frameadvance();
	gui.cleartext();
	gui.addmessage("snooped "..bizstring.fold(table.concat(buffer, " "), 60, "\n    "));
	buffer = {};
end

Read the linked RumbleTech.pdf and trace how SNES controller-register writes reach event.on_bus_write at 0x4016; compare that behavior with the stated bsnes support. Done means implementing SNES rumble support over the controller ports and verifying it against the standard.