Create SPA showcase for git-artifact hosted on GitHub Pages

[Copilot]

This PR implements a comprehensive Single Page Application (SPA) showcase for git-artifact that will be hosted on GitHub Pages. The showcase provides an interactive demonstration of the library's capabilities, making it easier for users to understand and adopt the tool.

🎯 Key Features

Interactive Demo Section

• Tabbed interface with 4 categories: Initialize, Add Artifact, Fetch Latest, and Find Artifacts
• Copy-to-clipboard functionality for all code examples with visual feedback
• Real command examples with detailed explanations and parameter descriptions

Visual Git History Concept

• Custom git graph diagram that clearly illustrates the "horizontal" commit history approach
• Visual representation showing how artifacts are stored using tags rather than stacked commits
• Responsive design that adapts to different screen sizes

Comprehensive Content

• Landing page with hero section highlighting key benefits (Fast & Efficient, CI/CD Ready, Cost Effective)
• Use cases section with 4 real-world scenarios including Library Distribution, CI/CD Pipeline Artifacts, Embedded Development, and Source Code Dependencies
• Complete API reference with all commands organized by category (Repository Management, Artifact Operations, Utility Commands)
• Step-by-step installation guide with quick start examples

Modern UI/UX

• Responsive mobile-first design with hamburger navigation for mobile devices
• Smooth scrolling navigation with active link highlighting based on scroll position
• Beautiful gradient hero section with feature cards and modern styling
• Hover effects and animations throughout for enhanced user experience

🛠️ Technical Implementation

The SPA is built with vanilla HTML, CSS, and JavaScript to ensure:

• No build dependencies - works directly with GitHub Pages
• Fast loading times with optimized assets
• Easy maintenance and future updates
• SEO optimization with proper meta tags and structured content

Files Added

• docs/index.html - Main SPA with all content sections
• docs/styles.css - Responsive CSS styling with mobile-first approach
• docs/script.js - Interactive JavaScript functionality
• docs/_config.yml - Jekyll configuration for GitHub Pages
• docs/favicon.svg - Custom favicon for branding
• docs/manifest.json - PWA manifest for app-like experience
• docs/README.md - Documentation for the showcase
• .github/workflows/deploy-pages.yml - GitHub Actions workflow for automatic deployment

🚀 Deployment

The showcase automatically deploys to GitHub Pages via the included GitHub Actions workflow. Once repository GitHub Pages settings are configured, it will be available at https://praqma.github.io/git-artifact/.

📱 Testing

The SPA has been thoroughly tested across:

• Desktop browsers at various screen resolutions
• Mobile devices with responsive breakpoints
• Interactive features including navigation, tabs, and copy functionality
• Accessibility with semantic HTML and keyboard navigation support

This implementation addresses all requirements from the original issue, providing a professional showcase that will significantly improve project visibility and user onboarding experience.

Fixes #27.

---

💬 Share your feedback on Copilot coding agent for the chance to win a $200 gift card! Click here to start the survey.