docs: add complexity analysis to insertion_sort docstring

Add Time Complexity (Best/Average/Worst) and Space Complexity
notes to sorts/insertion_sort.py, improving educational value
as requested in the issue.

Fixes #14866

Author: deepshekhardas

sorts/insertion_sort.py

@@ -31,6 +31,16 @@ def insertion_sort[T: Comparable](collection: MutableSequence[T]) -> MutableSequ
     comparable items inside
     :return: the same collection ordered by ascending
 
+    Complexity Analysis:
+        Time Complexity:
+            - Best Case: O(n) when the collection is already sorted
+            - Average Case: O(n^2)
+            - Worst Case: O(n^2) when the collection is sorted in reverse order
+
+        Space Complexity:
+            - O(1) because the algorithm sorts the collection in place and
+              uses only a constant amount of additional memory
+
     Examples:
     >>> insertion_sort([0, 5, 3, 2, 2])
     [0, 2, 2, 3, 5]