Improve URDFs and create simulations for the 3dof

..._2dof/simple_robot_2dof/forward_kinematics_node_2dof_1.py

ros2_ws/src/simple_robot_2dof/urdf/simple_robot.urdf

...t_3dof/launch/simple_robot_rviz_simulation_3dof_launch.py

...imple_robot_3dof/rviz/forward_kinematics_simulations.rviz

.../rviz/forward_kinematics_simulations.rviz:Zone.Identifier

ros2_ws/src/simple_robot_3dof/setup.py

..._3dof/simple_robot_3dof/forward_kinematics_node_3dof_1.py

..._3dof/simple_robot_3dof/forward_kinematics_node_3dof_2.py

ros2_ws/src/simple_robot_3dof/urdf/simple_robot.urdf