Bump purgecss from 5.0.0 to 6.0.0 in /wwwsrc

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:production
  update-type: version-update:semver-major
...

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

wwwsrc/package.json

@@ -10,7 +10,7 @@
     "cssnano": "^6.0.0",
     "cssnano-preset-advanced": "^6.0.0",
     "postcss-cli": "^11.0.0",
-    "purgecss": "^5.0.0",
+    "purgecss": "^6.0.0",
     "react": "^18.2.0",
     "react-bootstrap": "^2.8.0",
     "react-bootstrap-icons": "^1.10.2",