vercel.json

{
  "version": 2,
  "buildCommand": "echo 'No build needed'",
  "builds": [
    {
      "src": "api/**/*.js",
      "use": "@vercel/node",
      "config": {
        "includeFiles": "lib/**"
      }
    }
  ],
  "routes": [
    {
      "src": "/api/(.*)",
      "dest": "/api/$1.js"
    }
  ]
}