add Lua interactive Crash Course - Close #1518

free-courses-en.md

@@ -93,6 +93,7 @@
 * [Egghead.io](https://egghead.io/)
 
 ### Lua
+* [Lua Interactive Crash Course](http://luatut.com/crash_course.html)
 * [Lua Tutorial](http://www.tutorialpoint.com/lua/)
 * [Lua org](http://www.lua.org/)