docs: add Neon Functions adapter guide

[mezotv]

What

Adds a guide for running a Carbon bot on Neon Functions, and links it in the Adapters sidebar between Cloudflare Workers and Next.js.

Why

Neon Functions run web-standard fetch handlers on a long-lived Node.js runtime, which is the same handler shape Carbon's fetch adapter already produces. No new adapter is needed, but the setup (declaring the function in neon.ts, local dev, and deploy) isn't obvious from the generic Fetch page, so this walks through it.

Changes

• New page website/pages/v0.16.0/adapters/fetch/neon.mdx. It covers creating the handler, declaring the function in neon.ts, running locally with neon dev, and deploying with neon deploy. It also notes that Neon reads secrets from process.env directly, so the Cloudflare globalThis workaround isn't required.
• Sidebar entry in website/tome.config.mjs.

Notes

• Docs only. No framework code changed, so there's no changeset.
• Neon Functions are in beta and currently limited to the aws-us-east-2 region. The page flags this in a callout.

[changeset-bot]

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Latest commit: bc817a6

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