Transform clip path when applied to a group (#794)

* Transform clip path when applied to a group

Fix #136, #343, #566

* Golden test added

Author: FeodorFitsner

third_party/example/assets/simple/clip_path_transform.svg

@@ -1098,6 +1098,10 @@ class DrawableGroup implements DrawableStyleable, DrawableParent {
 
     if (style?.clipPath?.isNotEmpty == true) {
       for (Path clipPath in style!.clipPath!) {
+        if (transform != null) {
+          clipPath = clipPath.transform(transform!);
+        }
+
         canvas.save();
         canvas.clipPath(clipPath);
         if (children!.length > 1) {