updating DIRECTORY.md

Author: github-actions

DIRECTORY.md

@@ -85,6 +85,7 @@
  * [PascalTriangle](https://github.com/TheAlgorithms/Javascript/blob/master/Maths/PascalTriangle.js)
  * [PiApproximationMonteCarlo](https://github.com/TheAlgorithms/Javascript/blob/master/Maths/PiApproximationMonteCarlo.js)
  * [PrimeCheck](https://github.com/TheAlgorithms/Javascript/blob/master/Maths/PrimeCheck.js)
+ * [ReversePolishNotation](https://github.com/TheAlgorithms/Javascript/blob/master/Maths/ReversePolishNotation.js)
  * [SieveOfEratosthenes](https://github.com/TheAlgorithms/Javascript/blob/master/Maths/SieveOfEratosthenes.js)
 
 ## Project Euler