build(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

@@ -68,7 +68,7 @@
     "react-markdown": "^5.0.3",
     "react-router-dom": "^5.2.0",
     "react-syntax-highlighter": "^15.4.3",
-    "stylelint": "^13.9.0",
+    "stylelint": "^13.12.0",
     "stylelint-config-recommended": "^3.0.0",
     "stylelint-config-standard": "^20.0.0",
     "ts-jest": "^26.5.1",