Add xacro as a dependency (#152)

Author: ahtsan

robot_ws/src/hello_world_robot/package.xml

@@ -22,6 +22,7 @@
   <depend>turtlebot3_msgs</depend>
   <depend>turtlebot3_description</depend>
   <depend>turtlebot3_description_reduced_mesh</depend>
+  <depend>xacro</depend>
   <build_depend>message_generation</build_depend>
   <build_export_depend>message_runtime</build_export_depend>
   <exec_depend>message_runtime</exec_depend>