Add a page about SEO

SEO and meta tags lists what the Meta component emits. There is no page that walks through the whole picture: where titles and descriptions come from, how the sitemap and feeds are built, how OG images are produced, what is indexable and what is not, and which values a project must change after cloning the bootstrap.

Outline

• Page meta: title, description, canonical, noindex, lang, draft
• What Meta renders: OpenGraph, Twitter cards, article dates and authors
• Generated OG images and the og: 'generated' flag
• Sitemap page, XML sitemap appendix, JSON and XML feeds
• Structured data (Schema.org) and how to verify it
• Checklist for a new project: PROJECT_NAME, PROJECT_URL, PROJECT_DESCRIPTION, favicon, default OG image

Tasks

• Write the page under /features/ or a new /guides/ section
• Link it from the Features index and from the SEO feature page