Added wireplumber mixer widget

[AKArien]

The widget allows for control of the indivual volumes for sinks, sources and output streams, as well as selection of the default for the first two. Upon changes to a volume, it pops up an interactible slider for the volume that changed. Has mute on middle click, scroll to change volume and reduced view on right click Has the following settings :

• Popup on change : enable or disable the « popup on change » behavior
• Assignment of full mixer, reduced view and mute between left, middle and right click
• Timeout of popups
• Scroll sensitivity
• Reduced view / « quick action » target between : last changed volume, default sink, default source