feat: add health endpoint (#341)

Because

- We need /health endpoint to facilitate production

This commit

- add health endpoint

src/pages/api/health.tsx

@@ -0,0 +1,14 @@
+import { NextApiRequest, NextApiResponse } from "next";
+
+const handler = async (req: NextApiRequest, res: NextApiResponse) => {
+  const { method } = req;
+
+  if (method !== "GET") {
+    res.setHeader("Allow", ["GET"]);
+    res.status(405).end(`Method ${method} Not Allowed`);
+  }
+
+  return res.status(200).send("OK");
+};
+
+export default handler;