Issue Description:

The documentation for this standard library could be improved in a few ways. Discussion of modern constructor syntax for type conversions should be included (like `UInt32(value)` or `Int(value)` or whatever), as generally that is the preferred Swift language idiom over calling `numericCast`.

However, my main reason for filing the bug is the example code is outdated:

func random(in range: Range<Int>) -> Int {
    return numericCast(arc4random_uniform(numericCast(range.count)))
        + range.lowerBound
}

It uses `numericCast` twice in the context of creating a random number generation function. Clearly, this example was written before the standard library incorporated native random APIs. This example should be changed to something outside of the random number domain, as inventing `random(in🙂` functions ad-hoc (and especially calls to `arc4random_uniform`) from Swift should no longer be encouraged as good practice.