chore: add comment for is_static_element

Author: paoloricciuti

packages/svelte/src/compiler/phases/3-transform/client/visitors/shared/fragment.js

@@ -150,6 +150,8 @@ function is_static_element(node) {
 			return false;
 		}
 
+		// an img with loading lazy is not static but needs the `img` to be
+		// generated to be passed to `handle_lazy_img`
 		if (node.name === 'img' && attribute.name === 'loading') {
 			return false;
 		}