Update README for problem 75

Author: anirudhology

README.md

@@ -45,6 +45,7 @@ LeetCode solutions in Python
 | 72         | Edit Distance                                             | [Solution](problems/dynamic_programming/edit_distance.py)                                  | Medium     | Dynamic Programming                   |
 | 73         | Set Matrix Zeroes                                         | [Solution](problems/matrix/set_matrix_zeroes.py)                                           | Medium     | Matrix                                |
 | 74         | Search A 2D Matrix                                        | [Solution](problems/binary_search/search_a_2d_matrix.py)                                   | Medium     | Binary Search                         |
+| 75         | Sort Colors                                               | [Solution](problems/array/sort_colors.py)                                                  | Medium     | Array, Two Pointers                   |
 | 76         | Minimum Window Substring                                  | [Solution](problems/sliding_window/minimum_window_substring.py)                            | Hard       | Sliding Window                        |
 | 78         | Subsets                                                   | [Solution](problems/backtracking/subsets.py)                                               | Medium     | Backtracking                          |
 | 79         | Word Search                                               | [Solution](problems/backtracking/word_search.py)                                           | Medium     | Backtracking, DFS                     |