build(deps-dev): bump stylelint-config-standard from 20.0.0 to 21.0.0

Bumps [stylelint-config-standard](https://github.com/stylelint/stylelint-config-standard) from 20.0.0 to 21.0.0.
- [Release notes](https://github.com/stylelint/stylelint-config-standard/releases)
- [Changelog](https://github.com/stylelint/stylelint-config-standard/blob/master/CHANGELOG.md)
- [Commits](stylelint/stylelint-config-standard@20.0.0...21.0.0)

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

package.json

@@ -128,7 +128,7 @@
     "request": "2.88.2",
     "require-dir": "1.2.0",
     "stylelint": "13.12.0",
-    "stylelint-config-standard": "20.0.0",
+    "stylelint-config-standard": "21.0.0",
     "uncss": "0.17.3",
     "vinyl-buffer": "1.0.1",
     "vinyl-source-stream": "2.0.0",