docs: Add visual enhancements and improve README structure

[dvinix]

🎨 Visual Improvements to README

Enhanced the README with modern visual elements to improve developer experience and make the repository more attractive to contributors.

✨ Changes Made

Visual Elements Added

• ✅ Java Logo - Professional branding with official Java logo
• ✅ Mermaid Diagrams - Interactive flowcharts for usage and contribution workflows
• ✅ ASCII Art - Beautiful text boxes for features and section headers
• ✅ Tree Structures - Visual file-tree style for algorithm categories
• ✅ Icon Grid - Community links with icons (Discord, Issues, Website)
• ✅ Quick Navigation Bar - Top links for easy access to key sections

Layout Improvements

• ✅ Two-Column Tables - Better space utilization for examples and prerequisites
• ✅ Collapsible Section - "What's Inside?" expandable details for cleaner look
• ✅ Side-by-Side Examples - Code examples organized in columns
• ✅ Centered Elements - Key sections centered for better visual hierarchy

Content Organization

• ✅ Feature Highlights Box - ASCII art box showcasing key features
• ✅ Algorithm Categories - Visual tree structure for better understanding
• ✅ Contributing Workflow - Mermaid diagram showing Fork → Code → Test → PR → Merge
• ✅ Usage Flow - Diagram showing Import → Call → Result

🎯 Why These Changes?

1. Better First Impression - Modern, professional design attracts contributors
2. Improved Navigation - Quick links and clear sections help users find information
3. Visual Learning - Diagrams help understand workflows quickly
4. Professional Appeal - Makes the repository stand out
5. GitHub Native - Uses GitHub's built-in Markdown features
6. Mobile Friendly - Responsive layout works on all screen sizes

📊 Visual Elements

The README now includes:

• 🔷 Java logo for branding
• 📊 Interactive Mermaid flowcharts
• 🎨 ASCII art decorations
• 🌳 Tree structure visualizations
• 🖼️ Icon grid for community
• 📋 Two-column layouts

---

Checklist

• I have read CONTRIBUTING.md.
• This pull request is all my own work -- I have not plagiarized it.
• All filenames are in PascalCase. (N/A - Only README.md modified)
• All functions and variable names follow Java naming conventions. (N/A - No code changes)
• All new algorithms have a URL in their comments that points to Wikipedia or other similar explanations. (N/A - Documentation only)
• All new code is formatted with clang-format. (N/A - Documentation only)

Additional Checks:

• All original content and links preserved
• Visual elements render correctly on GitHub
• All badges and links are functional
• Layout is mobile-responsive
• Follows project documentation standards
• No code changes, documentation only

---

Note: This is a documentation-only PR focused on improving the README visual presentation and user experience. No algorithm code or functionality has been changed.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 75.81%. Comparing base (e6cb96f) to head (abc3667).
⚠️ Report is 4 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #6657      +/-   ##
============================================
+ Coverage     75.74%   75.81%   +0.06%     
- Complexity     5771     5803      +32     
============================================
  Files           702      705       +3     
  Lines         19770    19846      +76     
  Branches       3832     3851      +19     
============================================
+ Hits          14975    15046      +71     
- Misses         4215     4217       +2     
- Partials        580      583       +3     

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[DenizAltunkapan]

Thank you for your contribution! @divinixx . But the proposed README is too long and contains unnecessary sections like Algorithm Categories, because the DIRECTORY.md already shows which algorithms this repo already contains.