feat: wireplumber support

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)

resources/style.css

@@ -81,6 +81,7 @@ button:hover {
 #backlight,
 #network,
 #pulseaudio,
+#wireplumber,
 #custom-media,
 #tray,
 #mode,
@@ -176,6 +177,15 @@ label:focus {
     color: #2a5c45;
 }
 
+#wireplumber {
+    background-color: #fff0f5;
+    color: #000000;
+}
+
+#wireplumber.muted {
+    background-color: #f53c3c;
+}
+
 #custom-media {
     background-color: #66cc99;
     color: #2a5c45;