Add ROS2 templates

[JeremyZoss]

The ROS "New File" templates provided by QtCreator all seem to be ROS1-centric. Since ROS2 usage is increasing, it would be nice to have both "ROS1" and "ROS2" categories of templates.

[christian-rauch]

Correct. There are no ROS2 templates in the repo.

I personally never used the templates. I always used catkin to create new nodes. I am happy to review a PR if someone implements this. Creating a template is relatively easy. You only have to create the cpp file itself and a json that described that template. Have a look at the ROS1 templates: https://github.com/ros-industrial/ros_qtc_plugin/tree/devel/share/templates/wizards/files.