by jiangshan @jiangshanmeta
Implement a generic IsRequiredKey<T, K> that return whether K are required keys of T .
For example
type A = IsRequiredKey<{ a: number, b?: string },'a'> // true
type B = IsRequiredKey<{ a: number, b?: string },'b'> // false
type C = IsRequiredKey<{ a: number, b?: string },'b' | 'a'> // false
