This adds ability to get Pulseaudio current volume without calling an
external program. Also it provides a few other parameters like card's
current profile similarly to pavucontrol. Currently it only queries the
default sink (and associated card).
This us by far the most efficient as conky subscribe to a few pulseaudio
notifications. Whenever pulseaudio server changes (volume or default
sink or default card), conky's callback updates the results.