added underdeveloped but working image support (no freeing or samplers)

src/core/stack.rs

@@ -7,7 +7,7 @@ pub struct Stack {
 impl<Ctx> Widget<Ctx> for Stack {
     fn draw(&self, painter: &mut crate::Painter<Ctx>) {
         for child in &self.children {
-            painter.draw_within(child, painter.region);
+            painter.draw(child);
         }
     }
 }