Document iOS target configuration requirements for DAT apps

[gmays]

Summary

Adds README guidance for common iOS target configuration required by DAT integrations.

This documents the native app configuration values consumers need to verify when integrating the SDK outside a plain Xcode sample, including app link scheme registration, MWDAT keys, URL scheme querying, external accessory protocol, Bonjour/local network permissions, Bluetooth permissions, microphone/photo usage strings, and background modes.

Why

The current README explains how to add the package through Swift Package Manager, but it does not summarize the native iOS target configuration needed for registration, device discovery, and camera/media flows.

When integrating DAT into an Expo/React Native iOS app, missing or unclear plist/capability setup caused registration/device readiness failures and stale native builds. A checklist in the public README would reduce integration friction for other consumers.

Test Plan

Docs-only change. Verified the README Markdown with git diff --check and git diff --cached --check.

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