✨ Set up Copilot instructions for Canada.ca design system repository

.github/copilot-instructions.md

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+# GitHub Copilot Instructions
+
+## Project Context
+
+This repository contains the **Canada.ca Design System Library** ("Bibliothèque de conception Canada.ca"), which provides evidence-based design patterns, templates, and configuration guidance for Canadian government digital services.
+
+### Key Characteristics:
+- **Bilingual documentation**: All content must be provided in both French and English
+- **Jekyll-based site**: Uses Jekyll static site generator with YAML front matter
+- **Government standards**: Follows Canadian government digital service standards and accessibility requirements
+- **Design system**: Contains reusable design patterns, page templates, and implementation guidance
+
+## Development Guidelines
+
+### Language and Localization
+- Always provide content in both French and English when creating or modifying documentation
+- French content comes first, followed by English (following Canadian government language policy)
+- Use appropriate language codes: `fr` for French, `en` for English
+- Maintain consistent terminology across both languages
+- Reference existing bilingual content patterns in the repository for consistency
+
+### File Structure and Naming
+- Documentation files use `.md` extension for Markdown content
+- Page templates and layouts use `.html` extension
+- Follow the existing directory structure:
+  - `configurations-conception-communes/` - Common design configurations
+  - `modeles-obligatoire/` - Mandatory page templates  
+  - `modeles-recommandes/` - Recommended page templates
+  - `guide-redaction/` - Content writing guidance
+  - `communaute/` - Community and contribution guidance
+
+### Content Standards
+- Use clear, accessible language appropriate for government content
+- Follow the existing content patterns and documentation structure
+- Include implementation examples with working code snippets
+- Provide visual examples where appropriate
+- Reference official government sources and policies
+- Maintain consistency with Canada.ca style guide
+
+### Technical Requirements
+- Ensure HTML validation passes (uses vnu-jar for testing)
+- Follow Jekyll conventions for front matter and templating
+- Use semantic HTML markup
+- Maintain accessibility standards (WCAG compliance)
+- Test content with the existing build process
+
+### Code Style
+- Use consistent indentation (2 spaces for YAML, as per existing files)
+- Follow existing patterns for Jekyll includes and layouts
+- Use appropriate CSS classes matching the GC Web theme
+- Maintain clean, readable HTML structure
+
+### Design System Principles
+- Follow established design patterns from the Canada.ca design system
+- Maintain visual consistency across templates and components
+- Provide clear usage guidelines for each design pattern
+- Include "when to use" and "when not to use" guidance
+- Document implementation details for developers
+
+### Contribution Process
+- Reference the existing CONTRIBUTING.md for contribution guidelines
+- Follow the established workflow for design system changes
+- Consider the experimental → beta → stable progression for new patterns
+- Engage with the design system community for significant changes
+
+When working on this repository, always consider the broader impact on Canadian government digital services and maintain the high standards expected for official design system documentation.