Update vel_introductory_example.md

tutorials/python/vel_introductory_example.md

@@ -8,4 +8,4 @@ python3 cart_pos_ctrl_hls_solver.py
 
 This tutorial shows how to set up a fixed base robot (KUKA iiwa) to perform a simple Cartesian position control using velocity-level WBC. 
 
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+[[Previous Tutorial]](https://arc-opt.github.io/Documentation/tutorials/ros2_nullspace_control.html)[[Back to Main Page]](https://arc-opt.github.io/Documentation)[[Next Tutorial]](https://arc-opt.github.io/Documentation/tutorials/python/acc_rh5_legs_example.html)