Introduce WindowStream

[f1ames]

Feature description

Introduce WindowStream similar to WindowStream from v4:

In essence it's a stream of Array's containing a list of items - a window.

It would be a stream for moving window calculation with some simple methods.

Use case

Any data calculations which requires moving window (e.g. calculating moving averages).

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If you are interested in this issue or this stream type fits your use case, please upvote with :+1:.