Specify space complexity for merge sort (#11749)

* Added space complexity

Space complexity of merge sort is a key factor, when compared to quick sort

* Update merge_sort.py

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Co-authored-by: Maxim Smolskiy <mithridatus@mail.ru>

Author: IAteNoodles

sorts/merge_sort.py

@@ -18,6 +18,7 @@ def merge_sort(collection: list) -> list:
     :return: The same collection ordered in ascending order.
 
     Time Complexity: O(n log n)
+    Space Complexity: O(n)
 
     Examples:
     >>> merge_sort([0, 5, 3, 2, 2])