[Phase 1] Create custom landing page

[afucher]

Build the custom src/pages/index.astro landing page with hero, live demo, feature cards, version badge, and sponsorship.

Deliverable

A visually appealing landing page that introduces AstroChart, showcases a live chart demo, and drives users to installation + GitHub.

Acceptance Criteria

• src/pages/index.astro created (overrides Starlight default home)
• Hero section with:
  • Tagline: "A free and open-source JavaScript library for generating SVG astrology charts"
  • One-line description
  • npm install @astrodraw/astrochart snippet
  • "Get Started" CTA button (links to /docs/installation)
  • GitHub link
• Live demo section:
  • Renders a <ChartDemo> with radix + transit side by side (or a single complex demo)
  • Collapsible code block below showing the code that produced it
• Feature cards (3–4 cards):
  • "Pure SVG"
  • "Zero Dependencies"
  • "Fully Customizable"
  • "TypeScript-first"
• Current version badge:
  • Pulls version from package.json at build time
  • Displays as "v3.0.2"
  • Links to /docs/changelog
• Sponsorship section:
  • Ko-fi button
  • Text: "Support AstroChart"
  • Link to GitHub Sponsors
• Basic CSS styling (can be improved in Phase 2)
• Mobile responsive (works on 320px–1920px viewports)
• No console errors; deploys cleanly with Astro build

Related Plan Section

docs-plan.md §4.1 (Landing Page)