build: prepare for vercel (#388)

Author: gr2m

api/index.js

@@ -0,0 +1,23 @@
+const { createNodeMiddleware, createProbot } = require("probot");
+
+const app = require("../app");
+const probot = createProbot();
+const middleware = createNodeMiddleware(app, { probot });
+
+/**
+ * Redirect `GET /` to `/stats`, pass `POST /` to Probot's middleware
+ *
+ * @param {import('@vercel/node').NowRequest} request
+ * @param {import('@vercel/node').NowResponse} response
+ */
+module.exports = (request, response) => {
+  if (request.method !== "POST") {
+    response.writeHead(302, {
+      Location: "/stats",
+    });
+    response.end();
+    return;
+  }
+
+  middleware(request, response);
+};