add example query

dashboard/starter-example/app/query/route.ts

@@ -0,0 +1,26 @@
+// import { db } from "@vercel/postgres";
+
+// const client = await db.connect();
+
+// async function listInvoices() {
+// 	const data = await client.sql`
+//     SELECT invoices.amount, customers.name
+//     FROM invoices
+//     JOIN customers ON invoices.customer_id = customers.id
+//     WHERE invoices.amount = 666;
+//   `;
+
+// 	return data.rows;
+// }
+
+export async function GET() {
+	return Response.json({
+		message:
+			"Uncomment this file and remove this line. You can delete this file when you are finished.",
+	});
+	// try {
+	// 	return Response.json(await listInvoices());
+	// } catch (error) {
+	// 	return Response.json({ error }, { status: 500 });
+	// }
+}