Fixing documentation.

README.md

@@ -629,6 +629,11 @@ ros2 run lrs_exec tst_command --ros-args -r __ns:=/ex0 -p command:=test-turtle-2
 
 For how to test the ardupilot things with a copter see: https://gitlab.liu.se/lrs2/lrs_ardupilot/-/blob/main/README.md
 
+The implemntation of the executors and executor factories uses the
+TickedExecutor and TickedExecutorFactory classes.  This is probabky
+the most efficient way to implement executors when we have many
+executors and big TST trees
+
 ### 2.5 Plansys2
 
 For an example of integration with plansys2 see: https://gitlab.liu.se/lrs2/lrs_plansys2/-/blob/main/README.md