message: fix & dox: merged documentation and an example for LayerIndex and set cnstructor to take i32 to accept a negative value.
diff: use crate::*;
  +/// Styling to define the value on the `z` axis for an element. It does
  +/// translate to z-index in css.
  #[derive(Default)]
  pub struct LayerIndex<'a> {
  static_css_props: StaticCSSProps<'a>,
  @@ -12,6 +14,21 @@ impl<'a> LayerIndex<'a> {
  pub const MIN_VALUE: i32 = i32::MIN + Self::MAX_VALUE_OFFSET;
  pub const MAX_VALUE: i32 = i32::MAX - Self::MAX_VALUE_OFFSET;
  + pub fn new(index: i32) -> Self {
  + /// Set the layer index for an element.
  + /// # Example
  + /// ```no_run
  + /// use zoon::{named_color::*, *};
  + ///
  + /// let contained_items = Column::new()
  + /// .s(Background::new().color(GREEN_7))
  + /// .item(
  + /// Paragraph::new()
  + /// .s(LayerIndex::new(-1))
  + /// .content("Behind and trying to hide"),
  + /// )
  + /// .item(Paragraph::new().content("Front and you can see me"));
  + /// ```
  pub fn new(index: i32) -> Self {
  let mut this = Self::default();
  this.static_css_props
  