⬆️ upgrade react-markdown to v9

Author: renovate[bot]

package.json

@@ -18,7 +18,7 @@
     "nextra-theme-docs": "2.0.0-alpha.59",
     "react": "^18.2.0",
     "react-dom": "^18.2.0",
-    "react-markdown": "^8.0.3",
+    "react-markdown": "^9.0.0",
     "styled-components": "^5.3.5",
     "urlcat": "^2.0.4"
   },