chore(deps): upgrade @astrojs/mdx

Author: boneskull

package-lock.json

@@ -105,6 +105,7 @@
     "zod": "4.1.12"
   },
   "devDependencies": {
+    "@astrojs/mdx": "4.3.9",
     "@astrojs/starlight": "0.36.1",
     "@commitlint/cli": "20.1.0",
     "@commitlint/config-conventional": "20.0.0",