docs: show how to change the SolidStart dev port

[Janani-bn]

Closes #753

The defineConfig page now shows vinxi dev --port 3001 for changing the local dev port. It also notes that the flag can go in the package.json dev script, rather than defineConfig.

Checked the command against the Vinxi CLI docs and ran git diff --check. This is a docs-only change; no app tests were run.

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[amirhhashemi]

I appreciate you taking the time to do this. But I think the reference page for defineConfig is not a good place to add such info. This page should exclusively document defineConfig, and it doesn’t have a feature related to changing the port, AFAIK.

I get that the discussions in the referenced issue might have led you to do this. I’m sorry we haven’t done a proper review of that issue recently. I’ll take care of that right now.