32. implement RepeatString<T, C>


  - accepted / - tried

Similar to String.prototype.repeat(), implement RepeatString<T, C> to create a new type by repeating string T for C times.

type A = RepeatString<'a', 3> // 'aaa'
type B = RepeatString<'a', 0> // ''

There is no need to handle negative case of C.

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