[Collections\range] add documentation example

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https://github.com/arturo-lang/arturo/blob/046004606082468ef3e3f0d60a8672c61cb2a3ce/src/library/Collections.nim#L1413

            "step"  : ({Integer},"use step between range values")
        },
        returns     = {Range},
        # TODO(Collections\range) add documentation example
        #  labels: library, documentation, example
        example     = """
        ; range of :integers