by Anthony Fu @antfu
Implement a generic TupleToUnion<T> which covers the values of a tuple to its values union.
For example
type Arr = ['1', '2', '3']
type Test = TupleToUnion<Arr> // expected to be '1' | '2' | '3'풀이:
type TupleToUnion<T extends unknown[]> = T[number]
