feat(Tuples): add IndexOf

[wdhwg001]

Hi,

It's my first contribution to this repo, so please feel free to let me know if it doesn't follow any formatting / linting stuffs.

Basically it works like this:

type a = Call<T.IndexOf<2, [1, 2, 3]>> // 1
type b = Call<T.IndexOf<4, [1, 2, 3]>> // never

And it's particularly useful to be used with T.At.

[wdhwg001]

@gvergnaud Sorry to bother but would you like to leave a review?