v5.21.0 (improved scaling for large websites)

What's Changed

• feat: add canonical URL check by @Baspa in #96
• feat: add viewport meta tag check by @Baspa in #97
• feat: add character encoding check by @Baspa in #98
• feat: add favicon check by @Baspa in #99
• feat: add structured data (JSON-LD) check by @Baspa in #100
• feat: add Open Graph completeness check by @Baspa in #101
• feat: add Twitter card check by @Baspa in #102
• feat: add heading structure check by @Baspa in #103
• feat: add image dimensions check by @Baspa in #104
• feat: add lazy loading check by @Baspa in #105
• feat: add hreflang check by @Baspa in #106
• feat: add modern image format check by @Baspa in #107
• feat: add JSON output format (--format=json) by @Baspa in #108
• feat: add opt-in PageSpeed Insights checks (Core Web Vitals) by @Baspa in #109
• Bump dependabot/fetch-metadata from 2.5.0 to 3.1.0 by @dependabot[bot] in #111
• Bump actions/github-script from 8 to 9 by @dependabot[bot] in #110
• feat: add llms.txt check by @Baspa in #112
• feat: add AI crawler directives check (robots.txt) by @Baspa in #113
• feat: add XML sitemap check by @Baspa in #114
• feat: add HTTPS check by @Baspa in #116
• feat: add security headers check by @Baspa in #115
• feat: add redirect chain check by @Baspa in #117
• feat: scan models in chunks to keep memory flat by @Baspa in #118
• feat: batched queue scanning via seo:scan --queue by @Baspa in #119
• feat: parallel worker tuning for queued scans by @Baspa in #120

Full Changelog: v5.0.0...v5.21.0