update directory file for sliding windows

Author: Kesavan-77

DIRECTORY.md

@@ -322,6 +322,9 @@
   * [StringSearch](Search/StringSearch.js)
   * [TernarySearch](Search/TernarySearch.js)
   * [UnionFind](Search/UnionFind.js)
+* **Sliding-Windows**
+  * [MaxSumSubarrayFixed](Sliding-Windows/MaxSumSubarrayFixed.js)
+  * [LongestSubarrayWithSumAtMost](Sliding-Windows/LongestSubarrayWithSumAtMost.js)
 * **Sorts**
   * [AlphaNumericalSort](Sorts/AlphaNumericalSort.js)
   * [BeadSort](Sorts/BeadSort.js)