Draft: flatpak: Add libav and ffmpeg dependency
We need to build ffmpeg to add the G.722 encoder.
The current list of codecs are taken from https://gitlab.com/freedesktop-sdk/freedesktop-sdk/-/blob/master/elements/include/ffmpeg.yml excluding codecs I thought we don't need. @devrtz Can you help figure out the exact list of ffmpeg
codecs we need?
Fixes: #528 Build on top of !621 (merged)