Adds basic support for showing volume via wireplumber. Allows specifying
the node-id or falling back to the default Audio/Sink node id if node-id
is not set. If tooltip on hover is enabled, will show `{node_name}` by
default otherwise `tooltip-format`.
Format replacements:
`{volume}` - Volume in percentage
`{node_name}` - The node's nickname (`node.nick` property)
Sasha Moak