Update documentation of rqt_joint_trajectory_controller (#1578)

Author: AdityaPawar162

rqt_joint_trajectory_controller/doc/userdoc.rst

@@ -5,8 +5,17 @@
 rqt_joint_trajectory_controller
 ===============================
 
-rqt_joint_trajectory_controller is a GUI plugin for rqt that allows to command a joint_trajectory_controller.
+The rqt_joint_trajectory_controller provides an intuitive graphical way to test different joint positions and trajectories without having to manually construct complex trajectory messages or use command line interfaces.
 
 .. image:: rqt_joint_trajectory_controller.png
   :width: 400
   :alt: rqt_joint_trajectory_controller
+
+The interface allows you to:
+
+* Select the controller manager namespace and controller from dropdown menus.
+* Adjust target positions for joints (joint1 and joint2) using interactive sliders.
+* Fine-tune joint positions with precise numerical inputs.
+* Control the motion speed using the speed scaling slider.
+* Activate the trajectory execution with the central power button.
+* Visualize current joint configurations in real-time.