Description

As an environment author I might like to implement a factory function like:

export function createMyEnvironment(
  options: ...
) {
  return {
    dev: {
      ...
    },
    build: {
      ...
    },
    ...
  };
}

(example)

The problem here would be that no type checking nor autocompletion would be applied to the return type, so I might need to manually type dev, build etc... if I want to have type checking/autocompletion there (for example in my example notice how I had to set the createEnvironment arguments and return types).

There are also fields on the top environment object that I'd like to have types for too, such as consumer.

So I think it would be pretty convenient to expose the EnvironmentOptions type to vite users.

I am not sure if this was simply missed or exposing this type was considered but not done on purpose for some reason, I figured I could just open this PR and see what you guys say 🙂