docs: add Docusaurus website

[ngocdevv]

Summary

• add a Docusaurus 3.10.2 documentation website under docs/
• add a custom responsive landing page inspired by the information architecture and editorial rhythm of the React Native ExecuTorch website, while using original expo-share-content branding, visuals, copy, and assets
• document installation, architecture, delivery semantics, platform behavior, configuration, API, security limits, and troubleshooting
• add an immutable-SHA-pinned GitHub Pages workflow that validates pull requests and deploys merged documentation using Node 24-based official actions

Website

The landing page includes:

• sticky documentation navigation
• product hero with an original share-flow visualization
• supported content strip
• feature and use-case grid
• native intake → durable queue → acknowledgement architecture
• retryable import showcase with code sample
• Android, iOS, and web platform cards
• FAQ and final install CTA
• original logo, favicon, and Open Graph image
• responsive/reduced-motion behavior

The docs sidebar includes:

• Getting started
• Fundamentals
  • How it works
  • Delivery and file lifecycle
• Platforms
  • Android
  • iOS
  • Web
• Configuration
• API reference
• Security and limits
• Troubleshooting

Deployment

.github/workflows/deploy-docs.yml builds and deploys docs/build after documentation changes reach main.

Before the first deployment, set Repository settings → Pages → Build and deployment → Source to GitHub Actions.

Expected URL:

https://ngocdevv.github.io/React-Native-Share-Content/

Verification

Documentation:

• npm ci: pass
• npm run typecheck: pass
• npm run build: pass with no Docusaurus warnings
• actionlint: pass
• all 4 GitHub Actions pinned by immutable 40-character SHA
• official JavaScript Actions use Node 24; upload action is composite
• static crawl: 12 HTML pages and 262 internal links pass
• git diff --check: pass

Browser QA:

• desktop homepage: pass
• desktop docs shell/sidebar: pass
• 390 × 844 mobile homepage: pass
• mobile docs page: pass
• mobile navigation open/close: pass
• no horizontal overflow
• no missing image alt text
• no unnamed buttons or links
• no duplicate IDs
• one h1 per page
• homepage section deep links verified

Module regression gates:

• Jest: 6 suites, 39/39 tests pass
• ESLint: pass with zero warnings
• package build: pass