Add parameter to docs

Author: christophfroehlich

joint_trajectory_controller/doc/userdoc.rst

@@ -155,6 +155,11 @@ open_loop_control (boolean)
 
   Default: false
 
+cmd_timeout (double)
+  Timeout in seconds after which input command is considered staled. If zero, timeout is deactivated
+
+  Default: 0.0
+
 constraints (structure)
   Default values for tolerances if no explicit values are states in JointTrajectory message.