add comment for stopping the simulation

PathPlanning/ReedsSheppPath/reeds_shepp_path_planning.py

@@ -395,6 +395,7 @@ def test():
 
         if show_animation:  # pragma: no cover
             plt.cla()
+            # for stopping simulation with the esc key.
             plt.gcf().canvas.mpl_connect('key_release_event',
                     lambda event: [exit(0) if event.key == 'escape' else None])
             plt.plot(px, py, label="final course " + str(mode))