Bump purgecss from 2.2.1 to 2.3.0

Bumps [purgecss](https://github.com/FullHuman/purgecss) from 2.2.1 to 2.3.0.
- [Release notes](https://github.com/FullHuman/purgecss/releases)
- [Changelog](https://github.com/FullHuman/purgecss/blob/master/CHANGELOG.md)
- [Commits](https://github.com/FullHuman/purgecss/commits/v2.3.0)

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

package.json

@@ -47,7 +47,7 @@
     "linkinator": "^2.1.1",
     "npm-run-all": "^4.1.5",
     "postcss-cli": "^7.1.1",
-    "purgecss": "^2.2.1",
+    "purgecss": "^2.3.0",
     "shx": "^0.3.2",
     "stylelint": "^13.6.0",
     "stylelint-config-twbs-bootstrap": "^2.0.3",