feat(markdown): enable Satteri authoring features

www/package.json

@@ -20,6 +20,7 @@
     "generate:redirects": "node tools/generate-redirects.mjs"
   },
   "dependencies": {
+    "@astrojs/markdown-satteri": "^0.3.5",
     "@astrojs/mdx": "^7.0.5",
     "astro": "^7.1.5",
     "cheerio": "^1.1.0",