add docstring output to setconstraint! example

Author: franckgaga

src/predictive_control.jl

@@ -93,7 +93,14 @@ julia> mpc = LinMPC(setop!(LinModel(tf(3, [30, 1]), 4), uop=[50], yop=[25]));
 julia> mpc = setconstraint!(mpc, umin=[0], umax=[100], c_umin=[0.0], c_umax=[0.0]);
 
 julia> mpc = setconstraint!(mpc, Δumin=[-10], Δumax=[+10], c_Δumin=[1.0], c_Δumax=[1.0])
-
+LinMPC controller with a sample time Ts = 4.0 s, SteadyKalmanFilter estimator and:
+ 10 prediction steps Hp
+  2 control steps Hc
+  1 manipulated inputs u
+  2 states x̂
+  1 measured outputs ym
+  0 unmeasured outputs yu
+  0 measured disturbances d
 ```
 """
 function setconstraint!(