Implement the type version of Array.join, Join<T, U> takes an Array T, string or number U and returns the Array T with U stitching up.
type Res = Join<["a", "p", "p", "l", "e"], "-">; // expected to be 'a-p-p-l-e'
type Res1 = Join<["Hello", "World"], " ">; // expected to be 'Hello World'
type Res2 = Join<["2", "2", "2"], 1>; // expected to be '21212'
type Res3 = Join<["o"], "u">; // expected to be 'o'
import type { Equal, Expect } from '@type-challenges/utils'
type cases = [
Expect<Equal<Join<['a', 'p', 'p', 'l', 'e'], '-'>, 'a-p-p-l-e'>>,
Expect<Equal<Join<['Hello', 'World'], ' '>, 'Hello World'>>,
Expect<Equal<Join<['2', '2', '2'], 1>, '21212'>>,
Expect<Equal<Join<['o'], 'u'>, 'o'>>,
Expect<Equal<Join<[], 'u'>, ''>>,
Expect<Equal<Join<['1', '1', '1']>, '1,1,1'>>,
]