feat: Deploy to vercel

[chimon2000]

Description

Clearly describe what you are looking to add. The more context the better.

I would like the ability to deploy Dart Frog to Vercel. Although Vercel is mainly highlighted for use by frontend developers, it can be used to build serverless functions in Node.js, Go, Python, and Ruby, and allows developers to define custom runtimes: https://vercel.com/docs/runtimes#advanced-usage/developing-your-own-runtime

Requirements

• [ ] Implement a custom runtime for Vercel

Additional Context

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