Bump postcss from 8.5.3 to 8.5.6

Bumps [postcss](https://github.com/postcss/postcss) from 8.5.3 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@8.5.3...8.5.6)

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

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

Author: dependabot[bot]

package.json

@@ -22,7 +22,7 @@
     "cross-env": "7.0.3",
     "css-loader": "7.1.2",
     "mini-css-extract-plugin": "2.9.2",
-    "postcss": "8.5.3",
+    "postcss": "8.5.6",
     "postcss-loader": "8.1.1",
     "postcss-scss": "4.0.9",
     "sass": "1.86.0",