Nextra 4 migration

[moklick]

We want to migrate all sites (sites/xyflow.com, sites/svelteflow.dev, sites/reactflow.dev) to nextra 4. The reason why we want to migrate asap is that we would like to move the pro platform to the docs and be able to have one app (and one login) for everything.

Open Questions

• Do we want to use "Content Directory Convention" or "Page File Convention"

[dimaMachina]

list of subtasks

• use page.{jsx,tsx} instead of mdx pages with layout: 'raw' config in _meta, example
• remove getStaticProps usages instead of server components, example
• use builtin getPageMap function instead of getMdxContentUnderRoute
• use next.cofig.ts
• use turbopack next --turbopack flag
• use physical favicon svg instead of <link rel="icon" href={faviconSvgUrl} type="image/svg+xml" />