We do not need network connection to validate our appstream file.
Make it easier to run tests in containers that do not have network access.
Closes#307
Add missing PiP icons from web devel kit. Also add play/pause
icons at the right size and remove all workarounds/scaling
implemented or these two.
Playback icons are always two bars for pause and triangle for play,
so hopefully this will not be problematic, as this guaranties the
right size for them that Adwaita unfortunately cannot provide.
