Create announcement for React 18 migration

## Description

Create and publish announcements about the upcoming React 18 migration to inform users, stakeholders, and the community about the planned changes.

## Announcement Types

### Internal Communications
- **Team Notification**: Inform development teams about the migration timeline
- **Stakeholder Update**: Notify product owners and business stakeholders
- **Engineering Blog Post**: Technical deep-dive on the migration

### External Communications
- **GitHub Discussion**: Create discussion thread for community feedback
- **Migration Timeline**: Clear dates for Phase 1 (deprecation) and Phase 2 (breaking changes)
- **Support Channels**: Update documentation and support guides

## Content to Include

### Migration Timeline
- **Phase 1** (v8.x): Deprecation warnings, React 17 still supported
- **Phase 2** (v9.x): React 18 required, breaking changes, legacy package removed

### Benefits
- Security updates for React 18
- Performance improvements (concurrent features, automatic batching)
- Future-proofing with React ecosystem

### Migration Support
- Migration guide availability
- Support channels for questions
- Timeline for community feedback

## Channels for Announcement

### GitHub
- Create discussion in GitHub Discussions
- Update repository README with migration notice
- Pin the main migration issue

### Internal
- Teams channels (Slack, Teams)
- Engineering newsletters
- Product meetings

### Documentation
- Update main README with migration banner
- Create migration landing page
- Update getting started guides

## Implementation Steps

1. **Draft Announcements**
- Create templates for different audiences
- Get feedback from team leads
- Finalize messaging

2. **Schedule Communications**
- Coordinate timing across channels
- Ensure consistent messaging
- Plan follow-up communications

3. **Create Supporting Materials**
- Migration timeline graphics
- FAQ document
- Contact information for support

4. **Publish and Monitor**
- Post announcements across all channels
- Monitor feedback and questions
- Update based on community response

## Success Metrics
- Community engagement on GitHub discussions
- Questions answered via support channels
- Migration guide downloads/views
- Team awareness of timeline

## Labels
📚 documentation, 👾 React, 🚀 feature