Add new blank chat page to website

[Copilot]

Summary

Added a new blank page to the devcontainers.github.io website as requested. The page represents an empty chat session with 0 messages, providing a starting point for future chat functionality.

Changes

• New file: chat.md - A minimal blank page following Jekyll conventions
• URL: The page will be accessible at /chat when the site builds
• Layout: Uses the singlePage layout for consistency with other standalone pages

Implementation Details

The new page follows the exact same patterns as existing standalone pages in the repository:

• ✅ Proper Jekyll YAML frontmatter with title, layout, and section ID
• ✅ Consistent anchor structure matching other pages (overview.md, supporting.md)
• ✅ Uses singlePage layout template for proper styling and navigation
• ✅ Minimal content representing an empty chat state

File Structure

---
title: Chat
layout: singlePage
sectionid: chat
---

## Chat Session

Welcome to the chat session. No messages yet - start the conversation!

---

*This is a blank page ready for future chat functionality.*

Testing

• ✅ YAML frontmatter validation passed
• ✅ File structure matches existing page patterns
• ✅ Git commit successful with proper file tracking

The page is ready for the Jekyll build process and will integrate seamlessly with the existing website structure.

---

💬 Share your feedback on Copilot coding agent for the chance to win a $200 gift card! Click here to start the survey.