feat: add copy-to-clipboard button to code blocks (resolves #361)

[mhughes2012]

Overview

This PR implements a "Copy to Clipboard" functionality for all code blocks throughout the book. It uses a modern, language-agnostic icon approach to ensure the UI remains intuitive across all translated versions of the book without requiring additional i18n strings.

Key Changes

• Assets: Added website/copy-code.js and website/copy-code.css containing the logic and styling for the copy buttons.
• Layout Overrides: Modified _layouts/layout.html to inject these assets using basePath to ensure correct relative pathing on both the homepage and nested language chapters.
• Multi-language Support: To ensure the custom layouts are recognized by HonKit's multi-language build process, the _layouts folder has been included within each language directory (e.g., /en/, /fr/).
• Cross-Platform Compatibility: I opted to copy the layout files into the language subdirectories rather than using symlinks. This ensures that the build remains stable for contributors on Windows, where symlinks often fail or require elevated permissions.
• Build Configuration: Updated .bookignore to ensure .js assets are no longer excluded from the final output.

Technical Implementation Details

• Icons: Used embedded SVGs (overlapping squares) for the copy action and a checkmark for the success state. This removes dependencies on external icon fonts.
• Color Matching: The button background and hover states are tuned to match the existing #f7f7f7 code block background.
• Event Handling: The script hooks into GitBook/HonKit page.change events to ensure buttons are re-initialized when navigating between chapters without a full page reload.

Testing Performed

• Verified no errors on root homepage (localhost:4000).
• Verified on language sub-pages (e.g. localhost:4000/en/, http://localhost:4000/es/, http://localhost:4000/fr/).
• Tested "Copied!" success state and clipboard verification.
• Confirmed responsive behavior on mobile views.

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Project	Deployment	Actions	Updated (UTC)
learn-javascript	Ready	Preview, Comment	Feb 26, 2026 0:04am

[sumn2u]

LGTM! Thank you for adding this feature; readers will really benefit from it.

[sumn2u]

Resolves #367