Update README.md to include enhanced contributing section with GitHub-specific links, responsible AI guidance, comprehensive legal information, and Microsoft trademark notice.

Changes Needed

• Update Contributing section with emoji and direct links to GitHub issues/discussions
• Add Responsible AI section with link to Microsoft's Responsible AI standards
• Enhance Legal section with security policy reference and emoji
• Add Trademark Notice with Microsoft's brand guidelines

Acceptance Criteria

• Contributing section includes GitHub issues and discussions links
• Responsible AI section added with proper Microsoft link
• Legal section enhanced with security reference
• Trademark Notice section added
• All markdown linting passes
• Links validated and functional

Additional Context

This aligns the README with standard open-source project documentation practices and Microsoft's responsible AI commitments.