updating DIRECTORY.md

Author: github-actions

DIRECTORY.md

@@ -145,6 +145,7 @@
 ## Project-Euler
   * [Problem1](https://github.com/TheAlgorithms/Javascript/blob/master/Project-Euler/Problem1.js)
   * [Problem2](https://github.com/TheAlgorithms/Javascript/blob/master/Project-Euler/Problem2.js)
+  * [Problem6](https://github.com/TheAlgorithms/Javascript/blob/master/Project-Euler/Problem6.js)
 
 ## Recursive
   * [BinarySearch](https://github.com/TheAlgorithms/Javascript/blob/master/Recursive/BinarySearch.js)