feat: add zachleat.com-inspired theme enhancements

- Add time-difference web component for relative dates
- Add @zachleat/table-saw for responsive tables
- Add webmention facepile styling with bookmarks support
- Add OG image thumbnails to post navigation
- Add @11ty/is-land for lazy widget hydration
- Wrap sidebar widgets in is-land for deferred loading
- Lazy-load webmention avatars with is-land
- Add @zachleat/filter-container for blog archive filtering
- Add posting frequency sparkline to blog header
- Inline critical CSS and defer full stylesheet loading

package.json

@@ -14,11 +14,14 @@
     "@11ty/eleventy-img": "^6.0.0",
     "@11ty/eleventy-plugin-rss": "^2.0.2",
     "@11ty/eleventy-plugin-syntaxhighlight": "^5.0.2",
+    "@11ty/is-land": "^5.0.1",
     "@atproto/api": "^0.12.0",
     "@chrisburnell/eleventy-cache-webmentions": "^2.2.7",
     "@fontsource/inter": "^5.2.8",
     "@quasibit/eleventy-plugin-sitemap": "^2.2.0",
     "@resvg/resvg-js": "^2.6.2",
+    "@zachleat/filter-container": "^4.0.0",
+    "@zachleat/table-saw": "^1.0.7",
     "eleventy-plugin-embed-everything": "^1.21.0",
     "gray-matter": "^4.0.3",
     "html-minifier-terser": "^7.0.0",