refactor: make bridge key in useAsyncStoryblok optional

[m-shum]

• Makes bridge an optional key in UseAsyncStoryblokOptions. This seeks to remove the need to pass a redundant empty bridge options property in useAsyncStoryblok where bridge options are not needed.
• Removes duplicate declaration of UseAsyncStoryblokOptions interface from packages/nuxt/src/runtime/composables/useAsyncStoryblok.ts & imports it from packages/nuxt/src/types/index.ts instead to maintain a single source of truth
• Sets script setup lang to ts across /playground and /playground-e2e pages for clearer typescript error handling
• Updates the nuxt module's dev:prepare script in line with the Nuxt module builder (see here)
• Adds missing options keys in useAsyncStoryblok across /playground and /playground-e2e