ci: add preinstall script for vercel

Author: howard86

example/package.json

@@ -7,7 +7,8 @@
     "cypress": "cypress open",
     "cypress:headless": "cypress run",
     "e2e": "start-server-and-test start http://localhost:3000 cypress",
-    "e2e:headless": "start-server-and-test start http://localhost:3000 cypress:headless"
+    "e2e:headless": "start-server-and-test start http://localhost:3000 cypress:headless",
+    "preinstall": "cd .. && yarn install && yarn build"
   },
   "dependencies": {
     "next": "latest",