Add a Modal with Typed Navigation to a React Native App with React Navigation v6

We'll use the Stack Navigator from React Navigation v6 to display a modal for the story details page.

Then add TypeScript types for the navigation state to ensure correct typing.

Resources:

• React Navigation: https://reactnavigation.org/
• Stack Navigator: https://reactnavigation.org/docs/stack-navigator/

Checkpoint: Add a story details modal