Added an Elm Playground (#4689)

* Added Blockchain Programming Book

* Added the packt link

* Added a Kotlin Playground

* The Kotlin Playground

* Added a Flutter Playground

* Removed the Leadin Slash

* Added Ruby Playground

* Added a new line at the end of free programming playgrounds

* Fixed the spacing in free-programming-books-fa_IR.md

* Fixed More errors in the above file

* Errors fixed in free-programming-books-fa_IR.md

* Some more changes

* Restored the previous farsi file

* Added an Elm Playground

free-programming-playgrounds.md

@@ -75,6 +75,7 @@
 ### Elm
 
 * [Ellie](https://ellie-app.com)
+* [Try Elm!](https://elm-lang.org/try)
 
 
 ### Flutter
@@ -237,3 +238,5 @@
 * [Playground](https://www.typescriptlang.org/play/index.html)
 * [StackBlitz](https://stackblitz.com/fork/typescript)
 
+
+