Fix types in Svelte adapter

[pedroborges]

• Make setup callback optional for when in SSR mode

• Export ResolvedComponent type to be used in the resolve callback:

  createInertiaApp({
      resolve: (name) => resolvePageComponent(
          `./Pages/${name}.svelte`,
          import.meta.glob<ResolvedComponent>('./Pages/**/*.svelte')
      ),
      setup({ el, App }) {
          mount(App, { target: el})
      },
  })