With this change, one can initialize a ROS project by running:
nix flake init --template github:lopsided98/nix-ros-overlay
Besides adding the template, this commit also updates the README to
list the same template as the one from the flake. The listing in the
README can be easily updated to match the flake.nix file by running
the "mdsh" tool.
Previously, ros-core was not included presumably due to its dependency
on ros2doctor, which depended on ifcfg package unavailable in nixpkgs.
Since ros2cli version 0.17.0 (2022-01-25) ifcfg is no longer necessary
as it was replaced by psutils [1]. This means that we can use ros-core
without problems instead of manually specifying its dependencies such
ros-environment, ros2topic, etc.
In addition to ros-core, colcon is a basic tool for ROS 2. Include it
in the example too.
[1]: cc5d6b1f9b
