update readme

Author: hogan-tech

.github/test.txt

@@ -1,2 +1,3 @@
-3397-maximum-number-of-distinct-elements-after-operations python medium
-1625-lexicographically-smallest-string-after-applying-operations python medium
+3718-smallest-missing-multiple-of-k python easy
+3719-longest-balanced-subarray-i python medium
+3720-lexicographically-smallest-permutation-greater-than-target python medium

4080-smallest-missing-multiple-of-k/4080-smallest-missing-multiple-of-k.py renamed to Python/3718-smallest-missing-multiple-of-k.py

@@ -285,3 +285,6 @@
 | 3712 | [Sum of Elements With Frequency Divisible by K](https://leetcode.com/problems/sum-of-elements-with-frequency-divisible-by-k)                                           | [Python](./Python/3712-sum-of-elements-with-frequency-divisible-by-k.py)                      | [Easy](./Readme/3712-sum-of-elements-with-frequency-divisible-by-k.md)                        |
 | 3713 | [Longest Balanced Substring I](https://leetcode.com/problems/longest-balanced-substring-i)                                                                             | [Python](./Python/3713-longest-balanced-substring-i.py)                                       | [Medium](./Readme/3713-longest-balanced-substring-i.md)                                       |
 | 3715 | [Sum of Perfect Square Ancestors](https://leetcode.com/problems/sum-of-perfect-square-ancestors)                                                                       | [Python](./Python/3715-sum-of-perfect-square-ancestors.py)                                    | [Hard](./Readme/3715-sum-of-perfect-square-ancestors.md)                                      |
+| 3718 | [Smallest Missing Multiple of K](https://leetcode.com/problems/smallest-missing-multiple-of-k)                                                                         | [Python](./Python/3718-smallest-missing-multiple-of-k.py)                                     | [Easy](./Readme/3718-smallest-missing-multiple-of-k.md)                                       |
+| 3719 | [Longest Balanced Subarray I](https://leetcode.com/problems/longest-balanced-subarray-i)                                                                               | [Python](./Python/3719-longest-balanced-subarray-i.py)                                        | [Medium](./Readme/3719-longest-balanced-subarray-i.md)                                        |
+| 3720 | [Lexicographically Smallest Permutation Greater Than Target](https://leetcode.com/problems/lexicographically-smallest-permutation-greater-than-target)                 | [Python](./Python/3720-lexicographically-smallest-permutation-greater-than-target.py)         | [Medium](./Readme/3720-lexicographically-smallest-permutation-greater-than-target.md)         |