Fixed CSS linting with stylelint

.stylelintrc

@@ -6,6 +6,7 @@
   ],
   "rules": {
     "at-rule-empty-line-before": null,
+    "at-rule-no-unknown": null,
     "at-rule-no-vendor-prefix": true,
     "block-opening-brace-space-before": null,
     "block-closing-brace-newline-after": ["always", {

package.json

@@ -85,7 +85,7 @@
     "node-notifier": "^5.1.2",
     "postcss-pseudo-classes": "^0.2.0",
     "stylelint": "^8.0.0",
-    "stylelint-config-standard": "^16.0.0",
+    "stylelint-config-standard": "^17.0.0",
     "stylelint-order": "^0.6.0",
     "stylelint-scss": "^1.4.4",
     "through2": "^2.0.3",

yarn.lock

@@ -5429,9 +5429,15 @@ stylehacks@^2.3.2:
     text-table "^0.2.0"
     write-file-stdout "0.0.2"
 
-stylelint-config-standard@^16.0.0:
-  version "16.0.0"
-  resolved "https://registry.yarnpkg.com/stylelint-config-standard/-/stylelint-config-standard-16.0.0.tgz#bb7387bff1d7dd7186a52b3ebf885b2405d691bf"
+stylelint-config-recommended@^1.0.0:
+  version "1.0.0"
+  resolved "https://registry.yarnpkg.com/stylelint-config-recommended/-/stylelint-config-recommended-1.0.0.tgz#752c17fc68fa64cd5e7589e24f6e46e77e14a735"
+
+stylelint-config-standard@^17.0.0:
+  version "17.0.0"
+  resolved "https://registry.yarnpkg.com/stylelint-config-standard/-/stylelint-config-standard-17.0.0.tgz#42103a090054ee2a3dde9ecaed55e5d4d9d059fc"
+  dependencies:
+    stylelint-config-recommended "^1.0.0"
 
 stylelint-order@^0.6.0:
   version "0.6.0"