docs(stories): stop pin click propagation in image annotations example (#560)

Prevent click events from bubbling when placing a pin so the canvas click
handler does not clear the current draft selection.

Fixes #559

Co-authored-by: Giovanni Di Maggio <giovanni.dimaggio@digitouch.it>

Author: zovanni

src/stories/examples/image-annotations/example.tsx

@@ -839,6 +839,7 @@ function AnnotationCanvas(props: {
   const handlePinClick = useCallback(
     (e: React.MouseEvent) => {
       if (placeMode !== "pin") return;
+      e.stopPropagation();
       const pt = clientToContent(
         e.clientX,
         e.clientY,