fix(deps): update dependency @astrojs/mdx to v8

Author: renovate[bot]

package.json

@@ -31,7 +31,7 @@
   "dependencies": {
     "@astrojs/check": "^0.9.10",
     "@astrojs/markdown-remark": "^7.2.2",
-    "@astrojs/mdx": "^7.0.5",
+    "@astrojs/mdx": "^8.0.0",
     "@astrojs/rss": "^4.0.19",
     "@astrojs/sitemap": "^3.7.3",
     "@fontsource/fira-mono": "^5.3.0",