chore(package): update stylelint-config-standard to version 20.0.0

Closes #345

Author: greenkeeper[bot]

package.json

@@ -63,7 +63,7 @@
     "sinon": "^7.2.2",
     "strip-ansi": "^5.0.0",
     "stylelint": "^9.9.0",
-    "stylelint-config-standard": "^18.2.0",
+    "stylelint-config-standard": "^20.0.0",
     "tslint": "^5.12.0",
     "typescript": "^3.2.2",
     "vinyl": "^2.2.0",