Add esfiddle to free-programming-playgrounds.md (#4524)

* Add esfiddle

* Make alphabetical

* Remove / at the end of url

free-programming-playgrounds.md

@@ -116,6 +116,7 @@
 
 * [CodePen](https://codepen.io)
 * [CodeSandbox.io](https://codesandbox.io)
+* [Esfiddle](https://esfiddle.net)
 * [JSBin](http://jsbin.com)
 * [JSFiddle](http://jsfiddle.net)
 * [Plunker](http://plnkr.co)