Function install_tray 

pub fn install_tray(
    app: &App,
    tooltip: &str,
    menu: &Menu<Wry>,
    on_menu_item: impl Fn(&AppHandle, &str) + Send + Sync + 'static,
    on_left_click: impl Fn(&AppHandle) + Send + Sync + 'static,
) -> Result<()>

Install a tray icon using the app’s default window icon, with tooltip, menu, and the two behaviors every launcher-style tray needs: on_menu_item fires with the clicked item’s id; on_left_click fires on a tray-icon left click (mouse up).