updating DIRECTORY.md

Author: github-actions

DIRECTORY.md

@@ -162,6 +162,7 @@
   * [Haversine](https://github.com/TheAlgorithms/Javascript/blob/master/Navigation/Haversine.test.js)
 
 ## Project-Euler
+  * [Problem020](https://github.com/TheAlgorithms/Javascript/blob/master/Project-Euler/Problem020.js)
   * [Problem1](https://github.com/TheAlgorithms/Javascript/blob/master/Project-Euler/Problem1.js)
   * [Problem2](https://github.com/TheAlgorithms/Javascript/blob/master/Project-Euler/Problem2.js)
   * [Problem3](https://github.com/TheAlgorithms/Javascript/blob/master/Project-Euler/Problem3.js)