Add comprehensive syntax highlighting demo
Added complete_highlighting_demo.rs showing all highlighting features:
- Comments (single-line and multi-line)
- Keywords
- Identifiers
- Strings
- Numbers
- Regex
- Punctuation
- Brackets (unstyled)
- JSX syntax
Includes a color key showing all token types and their colors,
demonstrating full Babel babel-code-frame compatibility.
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude <noreply@anthropic.com>