Bump postcss from 8.5.5 to 8.5.6 in the dev-dependencies group

Bumps the dev-dependencies group with 1 update: [postcss](https://github.com/postcss/postcss).


Updates `postcss` from 8.5.5 to 8.5.6
- [Release notes](https://github.com/postcss/postcss/releases)
- [Changelog](https://github.com/postcss/postcss/blob/main/CHANGELOG.md)
- [Commits](postcss/postcss@8.5.5...8.5.6)

---
updated-dependencies:
- dependency-name: postcss
  dependency-version: 8.5.6
  dependency-type: direct:development
  update-type: version-update:semver-patch
  dependency-group: dev-dependencies
...

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

Author: dependabot[bot]

package-lock.json

@@ -63,7 +63,7 @@
     "metalsmith-tags": "^2.1.0",
     "moment": "^2.30.1",
     "npm-run-all": "^4.1.5",
-    "postcss": "^8.5.5",
+    "postcss": "^8.5.6",
     "postcss-cli": "^11.0.1",
     "postcss-preset-env": "^10.2.3",
     "striptags": "^3.2.0",