chore(deps-dev): css-loader cumulative deps and config update (#6596)

* css-loader@5
* postcss@8 peer dependency
* postcss-loader@4
* update webpack config with postcssOptions

package.json

@@ -123,7 +123,7 @@
     "copy-webpack-plugin": "^6.0.0",
     "cors": "^2.8.5",
     "cross-env": "=7.0.2",
-    "css-loader": "^4.0.0",
+    "css-loader": "=5.0.1",
     "cssnano": "=4.1.10",
     "cypress": "=5.5.0",
     "dedent": "^0.7.0",
@@ -159,7 +159,8 @@
     "npm-run-all": "^4.1.5",
     "oauth2-server": "^2.4.1",
     "open": "^7.0.4",
-    "postcss-loader": "^3.0.0",
+    "postcss": "=8.1.6",
+    "postcss-loader": "=4.0.4",
     "postcss-preset-env": "=6.7.0",
     "prettier": "^2.0.0",
     "raw-loader": "^4.0.0",

webpack/stylesheets.babel.js

@@ -31,11 +31,14 @@ export default {
           {
             loader: "postcss-loader",
             options: {
+              postcssOptions: {
                 sourceMap: true,
                 plugins: [
                   require("cssnano")(),
                   require("autoprefixer")(),
                 ],
+
+              }
             },
           },
           {