Update Indie stack to work with Vercel

[ItamarShDev]

What should I change to make this stack to work with Vercel?

I have tried to add the vercel.json file that works for me on other remix apps, and added the following line to remix.config.js

  serverBuildTarget: "vercel",

But though the build is successful, the app gets 500

[ItamarShDev]

Fixed it by installing @remix-run/vercel