Chore(deps-dev): bump purgecss from 5.0.0 to 6.0.0

Bumps [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: purgecss
  dependency-type: direct:development
  update-type: version-update:semver-major
...

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

package.json

@@ -77,7 +77,7 @@
     "expect": "^29.0.0",
     "mocha": "^10.1.0",
     "postcss": "^8.3.11",
-    "purgecss": "^5.0.0",
+    "purgecss": "^6.0.0",
     "relateurl": "^0.2.7",
     "rimraf": "^5.0.0",
     "srcset": "5.0.1",
@@ -88,7 +88,7 @@
   "peerDependencies": {
     "cssnano": "^6.0.0",
     "postcss": "^8.3.11",
-    "purgecss": "^5.0.0",
+    "purgecss": "^6.0.0",
     "relateurl": "^0.2.7",
     "srcset": "5.0.1",
     "svgo": "^3.0.2",