feat(vercel): add functions config

[smaeda-ks]

Currently, some serverless function options are not customizable, such as memory and maxDuration:
https://vercel.com/docs/build-output-api/v3#vercel-primitives/serverless-functions/configuration

This PR adds support so users can optionally set those options in their nitro.config.ts file:

// nitro.config.ts
import { defineNitroConfig } from 'nitropack'
export default defineNitroConfig({
  "vercel": {
        "functions": {
            "memory": 1024,
            "maxDuration": 10,
        }
    }
})

🔗 Linked issue

❓ Type of change

• 📖 Documentation (updates to the documentation or readme)
• 🐞 Bug fix (a non-breaking change that fixes an issue)
• 👌 Enhancement (improving an existing functionality like performance)
• ✨ New feature (a non-breaking change that adds functionality)
• ⚠️ Breaking change (fix or feature that would cause existing functionality to change)

📚 Description

📝 Checklist

• I have linked an issue or discussion.
• I have updated the documentation accordingly.

[pi0]

This is nice addition thanks! Any reason we don' allow specify all function configurations?

[codecov]

Codecov Report

Merging #976 (7e19ec1) into main (7efa31f) will increase coverage by 0.02%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #976      +/-   ##
==========================================
+ Coverage   67.77%   67.79%   +0.02%     
==========================================
  Files          60       60              
  Lines        6128     6132       +4     
  Branches      689      691       +2     
==========================================
+ Hits         4153     4157       +4     
  Misses       1966     1966              
  Partials        9        9              

Impacted Files	Coverage Δ
src/presets/vercel.ts	76.92% <100.00%> (+0.40%)	⬆️

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[smaeda-ks]

This is nice addition thanks! Any reason we don' allow specify all function configurations?

@pi0 Thanks for asking! Other options such as environment and regions should be managed in the project settings:
https://vercel.com/docs/concepts/projects/project-configuration#env

We recommend against using this property. To add custom Environment Variables to your Project define them in the Project Settings.

So adding memory and maxDuration would be enough, I believe.

[pi0]

Thanks again!