Using micro-ROS with rclcpp

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## Issue template

- Hardware description: Ubuntu 22.04 machine, compiling to flash on an Olimex_stm32_e407 board.
- RTOS: Zephyr
- Installation type: Follow the First micro-ROS Application on Zephyr guide from micro-ROS (link below), installing micro-ROS inside a docker container and creating the zephyr - olimex_stm32_e407 firmware with micro_ros_setup

https://micro.ros.org/docs/tutorials/core/first_application_rtos/zephyr/

- Version or commit hash: foxy version of micro_ros_setup

#### Steps to reproduce the issue
Hi, I want to use micro-ROS for building an application in c++, and needing rclcpp to compile. I have already figured out how to build and flash a C app using rcl/rclc, which I saw on the site are supported, but I can´t manage to do it with rclcpp.
From what I read on the site and the existing git issues, rclcpp is not yet supported officially by micro-ROS but is still a WIP, so I understand why it´s more complicated, but I also saw that several attempts have been made at implementing this, so I assume some solution/workaround is possible atm.

My understanding of the situation is that, after creating the firmware described above and configuring it for my application (made by copying a sample existing in the *firmware/zephyr_apps/apps/folder* , where all examples are), I should modify the CMakeLists.txt file and/or the .meta file in my application folder to make it include this rclcpp package, as it is present by default in the ros2 installation in */opt/ros/foxy/include/* folder. But, as I am a fairly new user to this, I couldn´t find the solution as to how to do it.

What steps should I follow ? Is my understanding of the situation right ? Should I look elsewhere to include this package ? Any help is appreciated, thank you in advance :)

#### Expected behavior
The code of my micro-ROS application in c++ should compile entirely. It is for now just a simple publisher code in c++, just like the one described in this tutorial :

https://docs.ros.org/en/foxy/Tutorials/Beginner-Client-Libraries/Writing-A-Simple-Cpp-Publisher-And-Subscriber.html

#### Actual behavior
It doesn´t build as it cannot find the "rclcpp/rclcpp.hpp" file because it is not included by default. I´m not including screenshots or logs because they are simple "cannot find rclcpp/rclcpp.hpp" reports, so unless I missed some critical info not much should come from it-

#### Additional information
As I am a fairly new user to micro-ROS and git, there may be some mistakes or elements missing in what I said. I am open to any request for more details, so don´t hesitate.

Inizia con la guida First micro-ROS Application on Zephyr e con l'applicazione copiata in firmware/zephyr_apps/apps. Esamina il relativo CMakeLists.txt e il file .meta, quindi riproduci l'errore di compilazione dovuto all'assenza di rclcpp/rclcpp.hpp nella configurazione Foxy basata su Docker. Il lavoro è completato quando una semplice applicazione publisher C++ viene compilata completamente per il target Olimex_stm32_e407.

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