Add news section for release notes and announcements

[yhk1038]

Summary

The T-Ruby documentation site currently lacks a dedicated section for project news and announcements. Adding a news section would help users stay informed about:

• Release notes and version updates
• Project announcements
• Important changes and breaking changes
• Community updates

Proposed Solution

Implement a news section using Docusaurus's blog plugin as a secondary instance:

• Route: /news
• Content type: Short-form updates (release notes, announcements)
• Features:
  • RSS/Atom feed support
  • Multi-language support (English, Korean, Japanese)
  • Dynamic tag system
  • No reading time display (content is short)

Implementation Details

1. Add @docusaurus/plugin-content-blog as a secondary plugin with id: 'news'
2. Create news/ directory for English content
3. Create i18n directories for Korean and Japanese translations
4. Update navbar to include "News" link
5. Update footer Resources section to include "News" link
6. Add sample news post for initial content

Benefits

• Centralized location for all project updates
• RSS feed for users to subscribe to updates
• Consistent with Docusaurus ecosystem
• Supports existing i18n infrastructure