Feature Request - Add ROS package.xml

[Ryanf55]

Is your feature request related to a problem?

When consuming exiv2 in ROS 2, it's standard practice to add a package.xml next to the top level CMakeLists of the project. Without it, dependencies must be manually installed, and build order manually maintained. Since ROS 2 does not yet support conan, rosdep can be viewed as an alternative.

Describe the solution you would like

• Add a package.xml to the root of this repo that details build and test dependencies for the default configuration options.
• Submit upstream rosdep PR (s) for any dependencies that do not already exist.

Describe alternatives you have considered

• Manage exiv2's dependencies manually in ROS 2
• Manage the build order of exiv2 relative to its consuming libraries manually in ROS 2
• Use an alternative package manager like conan - not supported by colcon yet

Desktop

• OS and version: Ubuntu 22.04, and others supported by rosdep
• Exiv2 version and source: 0.28.x
• Any software using exiv2 and source: closed source, but available for use with rosdep today due to some previous work: Add exiv2 for image metadata ros/rosdistro#37226

Additional context

• When installing dependencies with a ros based system, the tool rosdep is used, which reads the package.xml manifest and installs dependencies. It is OS-portable between many Linux distros, Mac, and Windows.
• When building multiple packages with the colcon build tool, the presence of a package.xml informs colcon on which order to build the packages
• A working CMake installation that supports find_package is a pre-requisite to using exiv2 in a colcon build system. Since that is working, there are no blockers to doing this work.
• Adding a package.xml should not break anything. It's a standalone file, so I'd request once this is merged, it is backported to 0.28.x.
• I can do the work for this PR, I would just like approval of the idea and it's something the exiv2 maintainers would support merging before I start the work.