feat: add dbus_connection() method to app::Application trait

src/app/action.rs

@@ -22,6 +22,8 @@ pub enum Action {
     Close,
     /// Closes or shows the context drawer.
     ContextDrawer(bool),
+    #[cfg(feature = "single-instance")]
+    DbusConnection(zbus::Connection),
     /// Requests to drag the window.
     Drag,
     /// Window focus changed