fix(deps): update dependency postcss to v8.4.28

Author: renovate[bot]

package-lock.json

@@ -70,7 +70,7 @@
     "image-minimizer-webpack-plugin": "3.8.3",
     "jest": "26.6.3",
     "mini-css-extract-plugin": "1.6.2",
-    "postcss": "8.4.27",
+    "postcss": "8.4.28",
     "postcss-custom-media": "10.0.0",
     "postcss-loader": "7.3.3",
     "postcss-rtlcss": "4.0.7",