fix: SEO support for the FxTS documentation site to improve search engine visibility

[hg-pyun]

Summary

This PR adds SEO support for the FxTS documentation site to improve search engine visibility.

Fixes #238

Changes

1. API Documentation SEO (Auto-generated)

Modified website/generate-api-docs/markdown-plugin/src/MarkdownFeature.ts to:

• Extract description from API documentation content
• Add description field to frontmatter automatically

2. Guide Pages SEO (Manual)

Added description frontmatter to all guide pages:

• getting-started.md
• function-composition.md
• lazy-evaluation.md
• handle-concurrency.md
• error-handling.md
• method-chaining.md
• to-async.md
• how-to-debug.md

3. VitePress SEO Meta Tags

Added transformPageData hook in website/docs/.vitepress/config.ts to dynamically generate meta tags:

• og:title
• og:description
• og:type
• og:image
• twitter:card
• twitter:title
• twitter:description
• twitter:image

Result

Before

Google search results showed only the generic description:

"A functional library for TypeScript/JavaScript programmers."

After

Each page now has its own unique meta tags:

<meta name="description" content="Returns Iterable/AsyncIterable of values by running each applying f.">
<meta property="og:title" content="map - FxTS">
<meta property="og:description" content="Returns Iterable/AsyncIterable of values by running each applying f.">
<meta property="og:type" content="website">
<meta property="og:image" content="https://fxts.dev/img/og_image.png">
<meta name="twitter:card" content="summary_large_image">
<meta name="twitter:title" content="map - FxTS">
<meta name="twitter:description" content="Returns Iterable/AsyncIterable of values by running each applying f.">
<meta name="twitter:image" content="https://fxts.dev/img/og_image.png">

[ppeeou]

cool 😎