Update theme toggle functionality and default theme settings

- Changed the default theme from light to dark mode in the theme toggle functionality.
- Updated the setup documentation to reflect the new default theme.
- Added Google Fonts integration for improved typography in the Hacktivity theme.
- Enhanced the lab layout with a theme toggle button for user convenience.

index.md

@@ -80,8 +80,8 @@ document.addEventListener('DOMContentLoaded', function() {
   const themeIcon = document.getElementById('theme-icon');
   const body = document.body;
   
-  // Check for saved theme preference or default to light mode
-  const currentTheme = localStorage.getItem('theme') || 'light';
+              // Check for saved theme preference or default to dark mode
+              const currentTheme = localStorage.getItem('theme') || 'dark';
   body.setAttribute('data-theme', currentTheme);
   updateThemeIcon(currentTheme);