Describe the bug
As far as I can tell there's no way to use sveltekit runtime imports (eg: $app/navigation) outside of sveltekit dev/build. Which makes testing virtually impossible. If there is a way to shim these imports outside of the main sveltekit context I haven't found it, so perhaps documentation is needed.

My particular use-case is with Storybook, where UI components that rely on any sveltekit modules break the whole setup. I tried aliasing them with webpack (pointing to .svelte-kit/dev/...) but that didn't work either.

Another use-case is publishing components for sveltekit that would need to rely on those imports.

To Reproduce

1. Setup storybook with Sveltekit
2. Create a component that imports a runtime module (eg: $app/env)
3. Run storybook and see if fail (cannot resolve module $app/env)

Severity
Not blocking, but makes building a component library with Storybook or other development/testing frameworks impossible. So, severe annoyance?