Array.pushのジェネリックバージョンを実装します。
例えば：
type Result = Push<[1, 2], '3'> // [1, 2, '3']
import type { Equal, Expect } from '@type-challenges/utils'
type cases = [
Expect<Equal<Push<[], 1>, [1]>>,
Expect<Equal<Push<[1, 2], '3'>, [1, 2, '3']>>,
Expect<Equal<Push<['1', 2, '3'], boolean>, ['1', 2, '3', boolean]>>,
]