chore(deps): update dependency postcss to v8.4.20

Author: renovate[bot]

package-lock.json

@@ -32,7 +32,7 @@
     "file-loader": "6.2.0",
     "html-webpack-plugin": "5.5.0",
     "mini-css-extract-plugin": "1.0.0",
-    "postcss": "8.4.19",
+    "postcss": "8.4.20",
     "postcss-loader": "7.0.2",
     "webpack": "5.75.0",
     "webpack-cli": "5.0.1",