chore(deps-dev): bump @fullhuman/postcss-purgecss from 5.0.0 to 6.0.0

Bumps [@fullhuman/postcss-purgecss](https://github.com/FullHuman/purgecss) from 5.0.0 to 6.0.0.
- [Release notes](https://github.com/FullHuman/purgecss/releases)
- [Changelog](https://github.com/FullHuman/purgecss/blob/main/CHANGELOG.md)
- [Commits](FullHuman/purgecss@v5.0.0...v6.0.0)

---
updated-dependencies:
- dependency-name: "@fullhuman/postcss-purgecss"
  dependency-type: direct:development
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

package-lock.json

@@ -37,7 +37,7 @@
     "@babel/cli": "^7.15",
     "@babel/core": "^7.15",
     "@babel/preset-env": "^7.15",
-    "@fullhuman/postcss-purgecss": "^5.0",
+    "@fullhuman/postcss-purgecss": "^6.0",
     "auto-changelog": "^2.3.0",
     "autoprefixer": "^10.3",
     "bootstrap": "^5.1",