docs: add iOS and Expo install troubleshooting

[markm39]

Goal

Add a short troubleshooting section for common first-install problems in React Native and Expo dev-client apps.

Context

Mobile Ink includes native iOS code, so first-time setup can fail in ways that are familiar to native React Native developers but confusing to new users.

Suggested Scope

• Add a troubleshooting section to README.md or a small doc under docs/.
• Cover that Expo Go is not supported and a dev client/prebuild is required.
• Mention that native changes require rebuilding the iOS app.
• Include common recovery steps such as cd ios && pod install, cleaning DerivedData, and restarting Metro.
• Include a note about the Reanimated/Worklets Babel plugin.

Done When

• A new user has a clear checklist for the most common install/setup failures.
• The docs stay generic to Mobile Ink and do not mention private app code.