Add Frame setters for rounding, margin and shadow

egui/src/containers/frame.rs

@@ -103,6 +103,22 @@ impl Frame {
         self
     }
 
+    pub fn corner_radius(mut self, corner_radius: f32) -> Self {
+        self.corner_radius = corner_radius;
+        self
+    }
+
+    /// Margin on each side of the frame.
+    pub fn margin(mut self, margin: impl Into<Vec2>) -> Self {
+        self.margin = margin.into();
+        self
+    }
+
+    pub fn shadow(mut self, shadow: Shadow) -> Self {
+        self.shadow = shadow;
+        self
+    }
+
     pub fn multiply_with_opacity(mut self, opacity: f32) -> Self {
         self.fill = self.fill.linear_multiply(opacity);
         self.stroke.color = self.stroke.color.linear_multiply(opacity);