message: doc: added an example for using IndexLayer with signal
diff: @@ -37,6 +37,26 @@ impl<'a> LayerIndex<'a> {
  this
  }
  + /// Set the layer index for an element depending on signal's state..
  + /// # Example
  + /// ```no_run
  + /// use zoon::{named_color::*, *};
  + ///
  + /// let (is_hovered, hover_signal) = Mutable::new_and_signal(false);
  + ///
  + /// let container = Column::new()
  + /// .s(Background::new().color(GREEN_7))
  + /// .item(
  + /// Paragraph::new()
  + /// .s(LayerIndex::with_signal(hover_signal.map_bool(|| 1, || -1)))
  + /// .content("Behind and trying to hide"),
  + /// )
  + /// .item(
  + /// Paragraph::new()
  + /// .content("Front and you can see me. Hover me so you can see a surprise")
  + /// .on_hovered_change(move |hover| is_hovered.set(hover)),
  + /// );
  + /// ```
  pub fn with_signal(
  index: impl Signal<Item = impl Into<Option<i32>>> + Unpin + 'static,
  ) -> Self {
  