Added dependency to socat (#527)

This is needed for the tool forwarding.

Author: Felix Exner (fexner)

ur_robot_driver/package.xml

@@ -53,6 +53,7 @@
   <exec_depend>robot_state_publisher</exec_depend>
   <exec_depend>ros2_controllers_test_nodes</exec_depend>
   <exec_depend>rviz2</exec_depend>
+  <exec_depend>socat</exec_depend>
   <exec_depend>urdf</exec_depend>
   <exec_depend>velocity_controllers</exec_depend>
   <exec_depend>xacro</exec_depend>