Add missing svelte.config.js

Author: lachlancollins

packages/svelte-query-devtools/svelte.config.js

@@ -0,0 +1,7 @@
+import { vitePreprocess } from '@sveltejs/vite-plugin-svelte'
+
+const config = {
+  preprocess: vitePreprocess(),
+}
+
+export default config