Update longpress.js

If the component gets destroyed before the timeout is cleared, you'll be invoking a method on a node that should not exist anymore

content/tutorial/03-advanced-svelte/04-actions/02-adding-parameters-to-actions/app-a/src/lib/longpress.js

@@ -16,6 +16,7 @@ export function longpress(node, duration) {
 
 	return {
 		destroy() {
+			clearTimeout(timer);
 			node.removeEventListener('mousedown', handleMousedown);
 			node.removeEventListener('mouseup', handleMouseup);
 		}