Added entry on Callback-group-level Executor in root README.md

Signed-off-by: Ralph Lange <ralph.lange@de.bosch.com>

Author: ralph-lange

Cpp/cbg-executor_ping-pong/README.md

@@ -1,6 +1,6 @@
 # cbg-executor_ping-pong_cpp
 
-This ROS2 package provides a small example for the use of the Callback-group-level Executor concept.
+This package provides a small example for the use of the Callback-group-level Executor concept.
 
 The Callback-group-level Executor leverages the callback-group concept in rclcpp by introducing real-time profiles such as RT-CRITICAL and BEST-EFFORT in the callback-group API (i.e. rclcpp/callback_group.hpp). Each callback requiring specific real-time guarantees, when created, may therefore be associated with a dedicated callback group. With this in place, the Executor class and depending classes (e.g., for memory allocation) were enhanced to operate at a finer, callback-group-level granularity.
 

README.md

@@ -384,3 +384,16 @@ rad0_display_c.exe
 cd C:\A\install\Lib\rad0_control_cpp\
 rad0_control_cpp.exe
 ```
+
+
+### Callback-group-level Executor
+
+Demo of the Callback-group-level Executor concept. See [Cpp/cbg-executor_ping-pong/README.md](Cpp/cbg-executor_ping-pong/README.md) for details.
+
+Run the micro-ROS Agent.
+
+```bash
+cd install/cbg-executor_ping-pong_cpp/bin/cbg-executor_ping-pong_cpp/
+./ping-pong --help  # to get all options
+./ping-pong io 1000 ...
+```