Add PDF download

[christophfroehlich]

Is your feature request related to a problem? Please describe.
From @yassine-cherni

Following the recent call for doc improvement ideas, I’d love to suggest a feature for ros2_control inspired by Yocto’s docs let users download all documentation for a ROS 2 distro (e.g., Jazzy) as a PDF. It’d simplify offline access for researchers and devs, avoiding online Rolling docs navigation.

Describe the solution you'd like
There is no built-in support, we have to use make latexpdf and add a downloadbutton

.. raw:: html

   <a class="btn primary" href="_static/yourdoc.pdf" download>Download PDF</a>

The difficulty is to install texlive with all dependencies for the gh action.