adds the wl output name as a css class

now you can have a custom styling for each bar

src/bar.cpp

@@ -17,6 +17,7 @@ waybar::Bar::Bar(struct waybar_output* w_output, const Json::Value& w_config)
   window.set_title("waybar");
   window.set_name("waybar");
   window.set_decorated(false);
+  window.get_style_context()->add_class(output->name);
 
   if (config["position"] == "right" || config["position"] == "left") {
     height_ = 0;