add examples to trajectory generation docs

docs/src/trajectory_planning.md

@@ -12,6 +12,35 @@ These both have output connectors of type `RealOutput` called `q, qd, qdd` for p
 
 See [Industrial robot](@ref) for an example making use of the [`point_to_point`](@ref) planner.
 
+
+## Example
+
+### Point-to-point trajectory
+```@example TRAJ
+using Multibody, Plots
+Ts = 0.001
+t = -1:Ts:3
+
+q1 = [1, 1.2] # Final point (2 DOF)
+qd_max = [0.7, 1.2] # Max velocity (2 DOF)
+qdd_max = [0.9, 1.1] # Max acceleration (2 DOF)
+q, qd, qdd = point_to_point(t; q1, qd_max, qdd_max)
+
+plot(t, [q qd qdd], ylabel=["\$q\$" "\$\\dot{q}\$" "\$\\ddot{q}\$"], layout=(3,1), l=2, sp=[1 1 2 2 3 3], legend=false)
+hline!([qd_max' qdd_max'], l=(2, :dash), sp=[2 2 3 3], c=[1 2 1 2], legend=false)
+```
+
+### 5:th order polynomial trajectory
+```@example TRAJ
+t = 0:Ts:3
+q1 = 1
+q, qd, qdd = traj5(t; q1)
+
+plot(t, [q qd qdd], ylabel=["\$q\$" "\$\\dot{q}\$" "\$\\ddot{q}\$"], layout=(3,1), l=2, legend=false)
+```
+
+
+
 ## Docstrings
 
 ```@index