LibWeb: Interpolate rect() function by computed value

Author: https://github.com/tcl3
Commit: 853bedeb31
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/6183
Reviewed-by: https://github.com/AtkinsSJ ✅

Libraries/LibWeb/CSS/Interpolation.cpp

@@ -1230,6 +1230,15 @@ static RefPtr<StyleValue const> interpolate_value_impl(DOM::Element& element, Ca
                     return {};
                 return Xywh { *interpolated_x, *interpolated_y, *interpolated_width, *interpolated_height };
             },
+            [&](Rect const& from_rect) -> Optional<BasicShape> {
+                auto const& to_rect = to_shape.get<Rect>();
+                auto from_rect_box = from_rect.box;
+                auto to_rect_box = to_rect.box;
+                auto interpolated_rect_box = interpolate_length_box(calculation_context, from_rect_box, to_rect_box, delta);
+                if (!interpolated_rect_box.has_value())
+                    return {};
+                return Rect { *interpolated_rect_box };
+            },
             [](auto&) -> Optional<BasicShape> {
                 return {};
             });