Implement Random.Zipf extension method

[AntyaDev]

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The Zipf distribution is a mathematical concept that describes the frequency of items ranked from most common to least common in a dataset, like word frequencies in a book or city populations.
Also, this distribution can be used to describe hot keys/items in database or popular tweets in Tweeter web service.

var stepIndex = context.Random.Zipf(n: 100, s: 1.0)