Update dependency postcss to ^8.4.38 (#103)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

package.json

@@ -32,7 +32,7 @@
     "next": "^13.5.6",
     "nextra": "3.0.0-alpha.13",
     "nextra-theme-docs": "3.0.0-alpha.13",
-    "postcss": "^8.4.21",
+    "postcss": "^8.4.38",
     "prettier": "^2.8.8",
     "pretty-quick": "^3.3.1",
     "prism-react-renderer": "^1.3.5",