Add playground section for Haskell (#2344)

Thanks!
* Add playground section for Haskell

Try Haskell https://www.tryhaskell.org/

* following markup rules

free-programming-playgrounds.md

@@ -36,6 +36,11 @@
 * [Echoplex](http://the-echoplex.net/flexyboxes/)
 
 
+### Haskell
+
+* [Try Haskell] (https://www.tryhaskell.org)
+
+
 ### JavaScript
 
 * [CodePen](http://codepen.io)