Add seq task usage example to docs (#475)

## Summary
Add example of how to use sequential tasks to existing Tasks concept
docs

Author: peterd-NV

docs/pages/concepts/concept_tasks_design.rst

@@ -107,3 +107,27 @@ Usage Examples
    destination_bin = asset_registry.get_asset_by_name("sorting_bin")()
 
    task = G1LocomanipPickAndPlaceTask(pick_object, destination_bin, galileo_scene)
+
+Sequential Tasks
+----------------
+
+Tasks can be composed sequentially to form longer horizon, more complex tasks using the ``SequentialTaskBase`` class.
+``SequentialTaskBase`` takes a list of ``TaskBase`` instances and automatically composes them into a single task.
+The order of the tasks in the list determines the order in which subtasks must be completed.
+
+**Usage Example (Pick and Place Task and Close Door Task Composition)**
+
+.. code-block:: python
+
+    pick_object = asset_registry.get_asset_by_name("mustard_bottle")()
+    destination = ObjectReference("refrigerator_shelf", parent_asset=kitchen)
+    pick_and_place_task = PickAndPlaceTask(pick_object, destination, kitchen)
+
+    openable_object = OpenableObjectReference("refrigerator", parent_asset=kitchen, openable_joint_name="fridge_door_joint")
+    close_door_task = CloseDoorTask(openable_object, closedness_threshold=0.10)
+
+    sequential_task = SequentialTaskBase(subtasks=[pick_and_place_task, close_door_task])
+
+**Available Examples**
+
+- **PutAndCloseDoorTask**: Pick up and move an object to a destination location and then close a door (within **GR1PutAndCloseDoorEnvironment**).