Add libsoup dependency

[fbe555]

Added libsoup as a build dependency.

Note that this requires the following addition to the ros index to come through first:
ros/rosdistro#40241

[BrettRD]

Amazing!
I think a similar index change might be required for jsonGLib

[fbe555]

Hi Brett.

I was in a bit of a hurry and only verified that the added dependency installed as intended 😅
It looks like both json-glib-1.0 and gstreamer-webrtc-1.0 needs to be installed. The first one can be installed throught the rosdep key libjson-glib, but the second one I think needs to be installed through the apt package libgstreamer-plugins-bad1.0-dev. I have tested that adding aforementioned dependency and manually installing the apt package leads to a successfull build on a freshly built container. I find the gstreamer plugin partitioning a bit confusing, but if you can confirm that the 'bad' set is needed, I'll add another entry to ros index and make another PR here with the two new dependencies.

Felix