Add an Expo and React Native integration package

Problem

GutenbergKit provides maintained Swift and Kotlin libraries, but React Native and Expo applications currently need to write and maintain their own native view bridges. The archived gutenberg-mobile project is not a reusable modern React Native package, and GutenbergKit is now the canonical mobile editor engine.

Proposal

Add a reusable Expo module package to this repository that:

• wraps EditorViewController on iOS and GutenbergView on Android;
• pins the package's native dependency to the matching GutenbergKit release;
• exposes initial title/content, editor readiness/errors, and explicit getTitleAndContent() retrieval;
• supports canonical serialized Gutenberg block markup;
• preserves host ownership of authentication, persistence, media selection, and autosaves;
• survives Expo prebuild through Expo Modules autolinking;
• documents iOS 17 / Swift tools 6.2 and Android API 24 requirements.

Initial scope

The first slice should be offline and intentionally exclude bearer tokens, REST persistence, media, plugin assets, and theme settings. Those can be additive props and delegates after the native lifecycle and content round trip are proven on both platforms.

Motivation

This gives React Native consumers a supported bridge without creating a parallel block editor or forking GutenbergKit. A working local Expo module prototype exists in Extra-Chill/extrachill-app#58 and can be extracted into this repository.

Start by reviewing the existing local Expo module prototype in Extra-Chill/extrachill-app#58, then trace the native entry points named in the proposal: EditorViewController on iOS and GutenbergView on Android. Done means a reusable offline package supports initial content, readiness and errors, explicit title/content retrieval, canonical block markup, Expo prebuild autolinking, and the stated iOS and Android requirements on both platforms.