Provide rosdep key for libserial-dev

See https://index.ros.org/d/libserial-dev/ . This is only used by feetech_ros2_driver, but I stumbled in it by looking at ros-physical-ai's demo pixi.toml : https://github.com/ros-physical-ai/demos/blob/25f5dddc5a32cbae69a903674dc13ed0309b2d35/pixi.toml#L152-L160 .

To workaround the fact that on conda-forge we do not have libserial-dev, they mix apt packages and conda packages, and it would be ideal if users do not do that for countless reasons.

To fix this, we would just need to package libserial-dev, but the situation is a bit complex on that: the upstream library https://github.com/wjwwood/serial is officially abandoned, see https://github.com/wjwwood/serial/issues/312 . I happen to mantain a friendly fork of that library as we use it in my organization at https://github.com/gbionics/serial_cpp, but that is not a drop-in replacement, so we can't package that in conda-forge and use it as a key for libserial-dev.

I think a possible strategy to deal with this is:

• Add an additional output to https://github.com/gbionics/serial_cpp to ensure that it can be a drop-in replacement for libserial-dev
• Package https://github.com/gbionics/serial_cpp in conda-forge
• Add a rosdep key for libserial-dev

fyi @sea-bass as you seem to be involved in https://github.com/ros-physical-ai/demos .

Start by reviewing the linked pixi.toml dependency entries, the serial_cpp repository, and the rosdep libserial-dev index page. The work is complete when serial_cpp provides a compatible additional output, it is packaged in conda-forge, and a rosdep key for libserial-dev resolves correctly.