feat: Header layouts and styling improvements

[eli64s]

This PR includes the following enhancements for improved README customization and styling:

Header Improvements:

• Added new header templates with modern, compact, and banner styles
• Introduced customizable SVG banners with gradient and theme support

Navigation & Structure:

• Implemented collapsible table of contents with multiple styles
• Added support for numbered, roman numeral, and bullet list formats
• Improved section anchors and internal link handling

Visual Customization:

• Added 20+ emoji theme packs for section headers
• Improved spacing and typography consistency

Documentation:

• Reorganized docs site with improved navigation
• Added detailed examples for header layouts and styling

Related Issues: None

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Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 90.19%. Comparing base (0ae4a8f) to head (27124b8).

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Additional details and impacted files

@@            Coverage Diff             @@
##             main     #127      +/-   ##
==========================================
+ Coverage   90.03%   90.19%   +0.16%     
==========================================
  Files          97       54      -43     
  Lines        3982     2692    -1290     
  Branches      246      262      +16     
==========================================
- Hits         3585     2428    -1157     
+ Misses        299      264      -35     
+ Partials       98        0      -98     

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