chore(deps-dev): bump stylelint from 13.9.0 to 13.12.0

Bumps [stylelint](https://github.com/stylelint/stylelint) from 13.9.0 to 13.12.0.
- [Release notes](https://github.com/stylelint/stylelint/releases)
- [Changelog](https://github.com/stylelint/stylelint/blob/master/CHANGELOG.md)
- [Commits](stylelint/stylelint@13.9.0...13.12.0)

Signed-off-by: dependabot[bot] <support@github.com>

package.json

@@ -47,7 +47,7 @@
     "lint-staged": "^10.5.3",
     "nightwatch": "^1.5.1",
     "prettier": "^2.2.1",
-    "stylelint": "^13.8.0",
+    "stylelint": "^13.12.0",
     "stylelint-config-prettier": "^8.0.2",
     "stylelint-config-standard": "^20.0.0"
   }