restore the tray feature in the desktop crate (#1475)

packages/desktop/Cargo.toml

@@ -56,6 +56,7 @@ tokio_runtime = ["tokio"]
 fullscreen = ["wry/fullscreen"]
 transparent = ["wry/transparent"]
 devtools = ["wry/devtools"]
+tray = ["wry/tray"]
 dox = ["wry/dox"]
 hot-reload = ["dioxus-hot-reload"]