Bump @fullhuman/postcss-purgecss from 5.0.0 to 6.0.0 in /wwwsrc

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

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

wwwsrc/package.json

@@ -3,7 +3,7 @@
   "version": "0.1.0",
   "private": true,
   "dependencies": {
-    "@fullhuman/postcss-purgecss": "^5.0.0",
+    "@fullhuman/postcss-purgecss": "^6.0.0",
     "bootstrap": "^5.3.1",
     "chart.js": "^4.2.0",
     "couch64": "^1.0.2",