Update README.md

Author: Walker30263

README.md

@@ -5,4 +5,6 @@ Solutions to Project Euler puzzles in JavaScript
 I noticed that most GitHub repositories about Project Euler puzzles have code in Python or Java, so this one is for JavaScript users!
 I'll try to make these in vanilla js without using any external libraries!
 
+# If you want, you can run these on [repl.it](https://repl.it/languages/nodejs), an online IDE
+
 Feel free to contribute if you find a more efficient/shorter/beginner-friendly way to solve problems!