by Anthony Fu @antfu
TypeScript 4.0 is recommended in this challenge
Implement a generic Last<T> that takes an Array T and returns its last element.
For example
type arr1 = ['a', 'b', 'c']
type arr2 = [3, 2, 1]
type tail1 = Last<arr1> // expected to be 'c'
type tail2 = Last<arr2> // expected to be 1풀이:
type Last<T extends any[]> = T extends [...infer R,infer L] ? L : never
