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

@@ -52,7 +52,7 @@
     "selenium-webdriver": "^4.0.0-beta.1",
     "sinon-chrome": "^3.0.1",
     "stylelint": "^13.12.0",
-    "stylelint-config-standard": "^20.0.0",
+    "stylelint-config-standard": "^21.0.0",
     "svelte": "^3.35.0",
     "svelte-accessible-dialog": "^2.1.2",
     "svelte-loader": "^3.0.0",