feat: add dark mode support across website and homepage

[mhughes2012]

Summary

This PR resolves issue #360 by improving dark mode behavior and styling across the site.

Changes

• fixed dark mode toggle behavior across page navigation
• added reusable dark mode script support
• ensured homepage dark mode assets are loaded correctly
• updated toggle icon behavior
• softened copy-code button styling in dark mode
• added dark mode styles for alert variants:
  • .alert-warning
  • .alert-info
  • .alert-success
  • .alert-danger
• added homepage dark mode styles for:
  • .language-selector-container
  • .language-card

Issue

Closes #360

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Project	Deployment	Actions	Updated (UTC)
learn-javascript	Ready	Preview, Comment	Mar 8, 2026 1:36am

[sumn2u]

@mhughes2012 Awesome work. The functionality is great, but I noticed a small issue on the landing page. Could you take a look?

Live preview: https://learn-javascript-git-fork-mhughes-0ab332-suman-kunwars-projects.vercel.app/

[mhughes2012]

@sumn2u thank you, I added a small update to address the background of the wider part of the page on the landing page.

[sumn2u]

LGTM!