docs: document Expo Router native setup

[nayounsang]

close mswjs/msw#2592

Please let me know if there is any additional context that needs to be included.

• A structure where the app register cannot be called after then.
• race condition between Expo Router registering the app and the initialization of MSW with import

I verified on my local machine using Expo Go that this approach works.

[vercel]

@nayounsang is attempting to deploy a commit to the MSW Team on Vercel.

A member of the Team first needs to authorize it.