The Index function performs a indexed access lookup on a type.
Example usage is shown below.
const T = Type.Object({
x: Type.Literal(1),
y: Type.Literal(2),
z: Type.Literal(3)
})
const S = Type.Index(T, Type.Union([ // const S: TUnion<[
Type.Literal('x'), // TLiteral<1>,
Type.Literal('y') // TLiteral<2>
])) // ]>