feat: Add func_touch

[Panzerhandschuh]

No description provided.

[jason-e]

trigger_multiple does have the Enable/Disable/Toggle inputs, but their descriptions use the word "trigger". I think you can override those like this (this is the same description func_brush has for Toggle):

Suggested change

	@SolidClass base(BaseEntityVisBrush, trigger_multiple)
	= func_touch: "A brush entity that triggers touch events."
	[
	]
	@SolidClass base(BaseEntityVisBrush, trigger_multiple, EnableDisable)
	= func_touch: "A brush entity that triggers touch events."
	[
	input Toggle(void) : "Toggle visibility/solidity of this brush."
	]