Update dependency postcss-loader to v8

Author: renovate[bot]

package-lock.json

@@ -23,7 +23,7 @@
     "html-webpack-plugin": "5.6.0",
     "mini-css-extract-plugin": "2.7.7",
     "postcss": "8.4.33",
-    "postcss-loader": "7.3.4",
+    "postcss-loader": "8.0.0",
     "sass": "1.70.0",
     "sass-loader": "13.3.3",
     "style-loader": "3.3.4",