Missing package.xml for newer ROS2 releases

[dsobek]

I've noticed that the wget command to fetch the package.xml file for newer distributions like humble doesn't work. Would it be possible to add a package.xml in this repository?
This makes working in projects where dependencies need to be built from source more difficult because tools such as rosinstall_generator and rosdep won't automatically find this package in the environment.

Looks like #80 could also solve this.

[sloretz]

Adding the package.xml to this repository seems fine to me. It's currently added via a patch during bloom-release when releases are made.

https://github.com/ros2-gbp/urdfdom_headers-release/blob/master/ros2/package.xml

[mikeferguson]

Should we instead just update the README.md? The link is wrong for the repo that has the package.xml (still ros-gbp instead of ros2-gbp)