Added Ruby Online Playground (#4623)

* 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

free-programming-books-fa_IR.md

@@ -87,3 +87,4 @@
 * [درس یادگیری ماشین دانشگاه استنفورد](https://maktabkhooneh.org/course/35-%DB%8C%D8%A7%D8%AF%DA%AF%DB%8C%D8%B1%DB%8C-%D9%85%D8%A7%D8%B4%DB%8C%D9%86-mk35/)
 * [درس یادگیری ماشین دانشگاه صنعتی شریف](https://maktabkhooneh.org/course/273-%DB%8C%D8%A7%D8%AF%DA%AF%DB%8C%D8%B1%DB%8C-%D9%85%D8%A7%D8%B4%DB%8C%D9%86-mk273/)
 
+

free-programming-playgrounds.md

@@ -194,6 +194,7 @@
 ### Ruby
 
 * [Codepad](http://codepad.org)
+* [TryRuby](https://try.ruby-lang.org)
 
 
 ### Rust
@@ -234,3 +235,4 @@
 
 * [Playground](https://www.typescriptlang.org/play/index.html)
 * [StackBlitz](https://stackblitz.com/fork/typescript)
+