ignore cmake projects

[stelzo]

The r2r project still uses CMake for building the nodes in the minimal node example. This PR ignores packages containing CMakeLists.txt to allow both libraries to be used for writing ROS nodes.

The plugin still can compile the r2r node but it leads to problems as described here. I don't really understand the need for colcon-cargo and colcon-ros-cargo at the same time as described in the ros2_rust Readme so I did the PR at both repositories. It seems like the relevant plugin for my system is colcon-ros-cargo though.