Use launch files (#832)

Co-authored-by: Sebastian Castro <[email protected]>

Author: Abishalini

doc/tutorials/pick_and_place_with_moveit_task_constructor/pick_and_place_with_moveit_task_constructor.rst

@@ -71,8 +71,8 @@ For all demos you should launch the basic environment: ::
 
 Subsequently, you can run the individual demos: ::
 
-  ros2 run moveit_task_constructor_demo cartesian
-  ros2 run moveit_task_constructor_demo modular
+  ros2 run moveit_task_constructor_demo cartesian.launch.py
+  ros2 run moveit_task_constructor_demo modular.launch.py
   ros2 launch moveit_task_constructor_demo pickplace.launch.py
 
 On the right side you should see the **Motion Planning Tasks** panel outlining the hierarchical stage structure of the tasks.