Default Worker Object for new modules format

[GregBrimble]

Maybe something like this:

declare interface CFWorker<Environment = Record<string, unknown>> {
  fetch(request: Request, env: Environment): Promise<Response>
}

Which would let a user:

declare type Environment = {
  MYKV: KVNamespace
}

export default {
  async fetch(request, env): Promise<Response> {
    await env.MYKV.put('key', 'value')
    return new Response('Hello, world!')
  },
} as CFWorker<Environment>