Add target="_blank" to external links in MDX

Use rehype-external-links plugin to automatically add target="_blank"
and rel="noopener noreferrer" to links pointing to external domains
(GitHub, Superhuman, Vimium, etc.).

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: ryan-williams

site/package.json

@@ -26,6 +26,7 @@
     "react-dom": "^19.2.0",
     "react-icons": "^5.5.0",
     "react-router-dom": "^7.11.0",
+    "rehype-external-links": "^3.0.0",
     "rehype-pretty-code": "^0.14.1",
     "rehype-raw": "^7.0.0",
     "remark-code-extra": "^1.0.1",

site/pnpm-lock.yaml

@@ -1,11 +1,19 @@
 import { defineConfig } from 'vite'
 import react from '@vitejs/plugin-react'
 import mdx from '@mdx-js/rollup'
+import rehypeExternalLinks from 'rehype-external-links'
 
 // https://vite.dev/config/
 export default defineConfig({
   plugins: [
-    { enforce: 'pre', ...mdx() },
+    {
+      enforce: 'pre',
+      ...mdx({
+        rehypePlugins: [
+          [rehypeExternalLinks, { target: '_blank', rel: ['noopener', 'noreferrer'] }],
+        ],
+      }),
+    },
     react({ include: /\.(jsx|js|mdx|md|tsx|ts)$/ }),
   ],
   resolve: {