fix: add execute tool to skill example (#182)

adk/middlewares/skill/main.go

@@ -52,6 +52,7 @@ func main() {
 	}
 	fsm, err := filesystem.New(ctx, &filesystem.MiddlewareConfig{
 		Backend:        be,
+		StreamingShell: be,
 	})
 	if err != nil {
 		log.Fatal(err)