feat: support Node.js as output

[aralroca]

WIP

Fixes #442
Fixes #195
Related #318

TODO:

• i18n is not working properly
• Check that redirects work correctly (trailing slash, etc.)
• RPC on navigation is not working correctly (issue with req.body)
• openEditor should not be called if the runtime is not Bun
• Server actions are not working
• Suspense is not working (u$ is not defined) - It’s an issue with VERSION_HASH between bun devandbun symlink`
• Test API routes
• Capture errors from the handler without crashing Node.js
• Investigate the output of Svelte/Astro's adapterNode, do they modify the output? What does it do?
• If output="node", build with Node target.
• Facilitate Custom Server + documentation
• Make bun start work with Node.js
• During the build, if it's Node, place server.js in build/server.js (constants should be hardcoded)
• Add documentation for handler and serve to API references
• Add tests for node handler. For now, I've added the first one, but the following are pending:
  • Fix the pipeline to pass this simple test
  • Fix the pipeline to see why so many Bun.js tests are failing now; it was cleaner before (8 Mac, 41 Linux)
  • Fix Windows test absolute path with file://
  • Add more tests to the handler, value tests, not just the simple proof-of-concept test
• Fix cookie handling
• add cert and key from config
• Document about WebSockets