fix(with-nuxt): a few changes to make it more idiomatic

a few changes to make the nuxt example more idiomatic - `<NuxtLayout>` wasn't being used - `ssr: false` is not required for static generation - rather, it means that there's no HTML rendered, and we advise against it even (especially!) when statically generating a site - `viewport` + `charset` are set by default - `useFetch` is typed so no need to specify the return type - `useRoute`, `defineCachedEventHandler` and so on are known to TS by the `tsconfig.json` - `@nuxt/devtools` does not need to be specified; it's enabled automatically