fix(segment): proxySrc, fileName for proxying

[georgekarapi]

❓ 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)
• ✨ New feature (a non-breaking change that adds functionality)
• 🧹 Chore (updates to the build process or auxiliary tools and libraries)
• ⚠️ Breaking change (fix or feature that would cause existing functionality to change)

📚 Description

Segment can be blocked through AdBlockers. One way to tackle it is using Self-hosted custom proxies (as mentioned here).

This PR introduces 2 options in Segment's config schema.

[vercel]

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[harlan-zw]

I don't think this quite makes sense as these aren't official Segment options, but maybe you can confirm with me.

As far as I know, there's already two workarounds available for this issue:

1. Use bundle: true, this will offload the script to be served by your Nuxt app, see (https://scripts.nuxt.com/docs/guides/bundling). This is by far the easiest option.
2. Set your own src using useScriptSegment({ scriptInput: { src: 'https://cdn.segment-proxy.com/analytics.js' } })

I'm not too sure where the proxy API tracking calls stubbing comes in as this seems embedded in the script itself.