feat(tray): multiple hosts

include/bar.hpp

@@ -26,6 +26,7 @@ class Bar {
     std::string output_name;
     uint32_t wl_name;
     bool visible = true;
+    uint32_t nb_tray_hosts = 0;
   private:
     static void handleLogicalPosition(void *, struct zxdg_output_v1 *, int32_t,
       int32_t);