Improve docstrings in insertion_sort.py to include complexity analysis

[dhruv-gautam-dev]

What would you like to share?

The insertion_sort() function in sorts/insertion_sort.py is missing
time and space complexity information in its docstring.

Proposed addition:

• Time Complexity: O(n^2) - worst and average case
• Time Complexity: O(n) - best case (already sorted)
• Space Complexity: O(1) - sorts in place

This helps students and developers understand the performance
characteristics of the algorithm.

Additional information

No response