feat: add markdown package to registry

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

index.json

@@ -23,6 +23,14 @@
       "versions": [
         {"version": "0.1.0", "checksum": "", "published_at": "2025-02-15", "yanked": false}
       ]
+    },
+    {
+      "name": "markdown",
+      "description": "Markdown to HTML converter for Lux",
+      "latest_version": "0.1.0",
+      "versions": [
+        {"version": "0.1.0", "checksum": "", "published_at": "2026-02-17", "yanked": false}
+      ]
     }
   ]
 }