message: Expose styling types for `scrollable` in `iced_web`
diff: //! Navigate an endless amount of content with a scrollbar.
  use crate::{bumpalo, css, Align, Bus, Column, Css, Element, Length, Widget};
  +pub use iced_style::scrollable::{Scrollbar, Scroller, StyleSheet};
  +
  /// A widget that can vertically display an infinite amount of content with a
  /// scrollbar.
  #[allow(missing_debug_implementations)]
  @@ -9,6 +11,7 @@ pub struct Scrollable<'a, Message> {
  height: Length,
  max_height: u32,
  content: Column<'a, Message>,
  + style: Box<dyn StyleSheet>,
  }
  impl<'a, Message> Scrollable<'a, Message> {
  @@ -24,6 +27,7 @@ impl<'a, Message> Scrollable<'a, Message> {
  height: Length::Shrink,
  max_height: u32::MAX,
  content: Column::new(),
  + style: Default::default(),
  }
  }
  @@ -85,6 +89,14 @@ impl<'a, Message> Scrollable<'a, Message> {
  self
  }
  + /// Sets the style of the [`Scrollable`] .
  + ///
  + /// [`Scrollable`]: struct.Scrollable.html
  + pub fn style(mut self, style: impl Into<Box<dyn StyleSheet>>) -> Self {
  + self.style = style.into();
  + self
  + }
  +
  /// Adds an element to the [`Scrollable`].
  ///
  /// [`Scrollable`]: struct.Scrollable.html
  @@ -112,6 +124,8 @@ where
  let width = css::length(self.width);
  let height = css::length(self.height);
  + // TODO: Scrollbar styling
  +
  let node = div(bump)
  .attr(
  "style",
  @@ -126,8 +140,6 @@ where
  )
  .children(vec![self.content.node(bump, bus, style_sheet)]);
  - // TODO: Complete styling
  -
  node.finish()
  }
  }
  