Using vite plugin node for svelte kit

[DarwinSenior]

Hi there,
I want to make this PR so that it is possible to use this plugin for @svelte/kit.

This pr in current form will create breakage to #25, but I would still like to introduce it so that it will play nicely with sveltekit.
Currently there is extensive discussion that the node adapter for the svelte kit is limited especially during the development.

Essentially, I want to pass next parameter to adapter function for the following usage:

async (app, req, res, next, server) => {
  // app here is fastify for example
  app.setDefaultRoute(() => next())
  await app.ready()
  app.routing(req, res)
}

The reason why it is necessary is that the sveltekit also mess with middleware. So that it remove the assumption that the vite-plugin-node is the end of all middleware.

I do hope you can consider this change as it greatly helps a lot of the discussion of sveltekit. For example sveltejs/kit#4654

[axe-me]

hi @DarwinSenior, thank you for your contribution. I'm planning to do some issue cleanup and bug fix this weekend.

Not sure if you can wait 2~3 days for me. This PR indeed will introduce some braking changes to this plugin. I may need to bump the major version of this plugin after merging this.

[DarwinSenior]

I see that the new ways to include next. Thanks. I will close this issue now