added lua function test item

doc/examples/example_simple.tum

@@ -5,13 +5,21 @@ main:
     steps:
 
       - py_func:
-          name: function test item
-          doc: The purpose of this step is to demonstrate func test item
+          name: python function call
+          doc: The purpose of this step is to demonstrate the py_func test item
           file: utils.py
           func_name: funcToBeExecuted
           param:
               - 123
 
+      - lua_func:
+          name: lua function call
+          doc: The purpose of this step is to demonstrate the lua_func test item
+          file: lua_func.lua
+          func_name: func_to_be_executed
+          param:
+              - 123
+
       - sleep:
           name: sleep item
           dialog: True

doc/examples/lua_func.lua

@@ -0,0 +1,6 @@
+tm = require("tm")
+
+function func_to_executed(param)
+    -- return tm.gd(param)
+    return param
+end