BuiltIns: adds void

[Emiyaaaaa]

• Fixed ReadonlyDeep turns void into unknown #781

and I had another thought that should we put void into Primitive? I think void is a primitive type same as undefined in TS, but void is not primitive value at Primitive's document.

How about your thoughts? @sindresorhus

[sindresorhus]

and I had another thought that should we put void into Primitive? I think void is a primitive type same as undefined in TS, but void is not primitive value at Primitive's document.

void is techincally not a primitive. In TS it kinds acts like one as a type, but I think it would be techincally incorrect to put it in Primtiive. Let's keep it in Builtins for now. We can consider moving it into Primitive later on if there's any need for it (it's risky as it could break things in the wild).