LibWeb: Add SVG <rect> element and test case :^)

Author: https://github.com/AtkinsSJ
Commit: 1dde6a0a2b
Pull-request: https://github.com/SerenityOS/serenity/pull/12444
Reviewed-by: https://github.com/awesomekling

Userland/Libraries/LibWeb/SVG/SVGRectElement.idl

@@ -0,0 +1,9 @@
+[Exposed=Window]
+interface SVGRectElement : SVGGeometryElement {
+    // [SameObject] readonly attribute SVGAnimatedLength x;
+    // [SameObject] readonly attribute SVGAnimatedLength y;
+    // [SameObject] readonly attribute SVGAnimatedLength width;
+    // [SameObject] readonly attribute SVGAnimatedLength height;
+    // [SameObject] readonly attribute SVGAnimatedLength rx;
+    // [SameObject] readonly attribute SVGAnimatedLength ry;
+};