fix sandbox

Author: Rich-Harris

playgrounds/sandbox/vite.config.js

@@ -11,7 +11,10 @@ export default defineConfig({
 		inspect(),
 		svelte({
 			compilerOptions: {
-				hmr: false
+				hmr: false,
+				experimental: {
+					async: true
+				}
 			}
 		})
 	],