Add a ColdFusion playground (#9078)

* Add ColdFusion book

* Fix order.

* Escape < > chars.

* Add a ColdFusion playground.

more/free-programming-playgrounds.md

@@ -6,6 +6,7 @@
 * [C#](#csharp)
 * [C++](#cpp)
 * [ClojureScript](#clojurescript)
+* [ColdFusion](#coldfusion)
 * [Crystal](#crystal)
 * [Dart](#dart)
 * [Docker](#docker)
@@ -90,6 +91,11 @@
 * [Web REPL](http://clojurescript.net)
 
 
+### ColdFusion
+
+* [TryCF](https://trycf.com)
+
+
 ### Crystal
 
 * [Compile & run code in Crystal](https://play.crystal-lang.org/#/cr)