How can we create a floating window by iced？

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my example code is this：

mod app;

use iced::{Size, Theme};
use crate::app::App;
use iced::window::Level;

pub fn main() -> iced::Result {
    iced::application("title", App::update,App::view)
        .window_size(Size::new(150.0,75.0))
        .decorations(false)
        .transparent(true)
        .level(Level::AlwaysOnTop)
        .resizable(false)
        .antialiasing(true)
        .run()
}

when i run it, an default icon was displayed in my dock.
image

how can i hide this？