Merge pull request #1131 from ChristianMurphy/renovate/postcss-8.x

chore: update dependency postcss to v8.5.9

Author: renovate[bot]

package-lock.json

@@ -52,7 +52,7 @@
     "eslint-plugin-markdown": "3.0.1",
     "husky": "8.0.3",
     "npm-run-all2": "8.0.4",
-    "postcss": "8.5.8",
+    "postcss": "8.5.9",
     "postcss-less": "6.0.0",
     "postcss-nested": "7.0.2",
     "postcss-scss": "4.0.9",