js(tutorial): add note about CVAT integration

Author: alalek

doc/js_tutorials/js_imgproc/js_intelligent_scissors/js_intelligent_scissors.markdown

@@ -7,6 +7,8 @@ Goal
 - Here you can check how to use IntelligentScissors tool for image segmentation task.
 - Available methods and parameters: @ref cv::segmentation::IntelligentScissorsMB
 
+@note The feature is integrated into [CVAT](https://github.com/openvinotoolkit/cvat) annotation tool and you can try it online on https://cvat.org
+
 \htmlonly
 <iframe src="../../js_intelligent_scissors.html" width="100%"
         onload="this.style.height=this.contentDocument.body.scrollHeight +'px';">