Add overlay support in iced_pure and port PickList 🎉

pure/src/widget/scrollable.rs

@@ -1,3 +1,4 @@
+use crate::overlay;
 use crate::widget::tree::{self, Tree};
 use crate::{Element, Widget};
 
@@ -230,6 +231,19 @@ where
             },
         )
     }
+
+    fn overlay<'b>(
+        &'b mut self,
+        tree: &'b mut Tree,
+        layout: Layout<'_>,
+        renderer: &Renderer,
+    ) -> Option<overlay::Element<'b, Message, Renderer>> {
+        self.content.as_widget_mut().overlay(
+            &mut tree.children[0],
+            layout.children().next().unwrap(),
+            renderer,
+        )
+    }
 }
 
 impl<'a, Message, Renderer> From<Scrollable<'a, Message, Renderer>>