Update release notes

Author: saikishor

doc/release_notes.rst

@@ -156,6 +156,7 @@ hardware_interface
 * With (`#1683 <https://github.com/ros-controls/ros2_control/pull/1683>`_) the ``rclcpp_lifecycle::State & get_state()`` and ``void set_state(const rclcpp_lifecycle::State & new_state)`` are replaced by ``rclcpp_lifecycle::State & get_lifecycle_state()`` and ``void set_lifecycle_state(const rclcpp_lifecycle::State & new_state)``. This change affects controllers and hardware. This is related to (`#1240 <https://github.com/ros-controls/ros2_control/pull/1240>`_) as variant support introduces ``get_state`` and ``set_state`` methods for setting/getting state of handles.
 * With (`#1421 <https://github.com/ros-controls/ros2_control/pull/1421>`_) a key-value storage is added to InterfaceInfo. This allows to define extra params with per Command-/StateInterface in the ``.ros2_control.xacro`` file.
 * With (`#1763 <https://github.com/ros-controls/ros2_control/pull/1763>`_) parsing for SDF published to ``robot_description`` topic is now also supported.
+* With (`#1567 <https://github.com/ros-controls/ros2_control/pull/1567>`_) all the Hardware components now have a fully functional asynchronous functionality, by simply adding ``is_async`` tag to the ros2_control tag in the URDF. This will allow the hardware components to run in a separate thread, and the controller manager will be able to run the controllers in parallel with the hardware components.
 
 joint_limits
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