Add Common Terms glossary page to the devcontainers website

[Copilot]

This PR adds a new Common Terms page to the Development Containers website to help users understand key terminology used throughout the specification and documentation.

What's Added

• New Terms Page: Created terms.md with comprehensive definitions for 16 common terms including:

  • Development Container / Dev Container
  • devcontainer.json
  • Features and Templates
  • Container images and base images
  • OCI Registry
  • Lifecycle scripts
  • Workspace concepts
  • And more...

• Navigation Integration: Added the Terms page to the main navigation menu in _includes/topnav.html

Features

• Alphabetical Organization: Terms are organized alphabetically for easy reference
• Anchor Links: Each term has its own anchor link for direct navigation and sharing
• Consistent Styling: Uses the same singlePage layout as other informational pages
• Comprehensive Coverage: Covers the most frequently used terms from the specification

Testing

• ✅ Jekyll build passes successfully
• ✅ Generated HTML renders correctly with proper navigation
• ✅ All anchor links work for internal navigation
• ✅ Terms page is accessible via /terms URL
• ✅ Navigation shows active state when on the Terms page

This addresses the need for a centralized glossary to help both new and experienced users understand the terminology used throughout the dev container ecosystem.

Warning

Firewall rules blocked me from connecting to one or more addresses

I tried to connect to the following addresses, but was blocked by firewall rules:

• esm.ubuntu.com
  • Triggering command: /usr/lib/apt/methods/https (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to my firewall allow list

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