Set up GitHub Pages for documentation site

[zp6]

Changes

Implements #21 - deploys VitePress docs to GitHub Pages.

1. GitHub Actions workflow (.github/workflows/docs.yml)

• Triggers on push to main when docs/ or workflow file changes
• Supports manual workflow_dispatch trigger
• Builds VitePress site and deploys to GitHub Pages
• Uses actions/deploy-pages@v4 with proper permissions

2. VitePress search (docs/.vitepress/config.mjs)

• Enabled built-in local search via themeConfig.search.provider: 'local'

Setup Required

After merging, the repo admin needs to:

1. Go to Settings > Pages
2. Set Source to GitHub Actions
3. The workflow will deploy automatically on next push to main

Fixes #21

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Wallet: zp6