Update dependency stylelint-config-standard to v21

Author: renovate-bot

package-lock.json

@@ -11,7 +11,7 @@
     "postcss-cli": "8.3.0",
     "postcss-reporter": "6.0.1",
     "stylelint": "13.12.0",
-    "stylelint-config-standard": "20.0.0",
+    "stylelint-config-standard": "21.0.0",
     "supertest": "6.1.3"
   },
   "scripts": {