build(deps-dev): bump postcss from 8.5.12 to 8.5.15

Bumps [postcss](https://github.com/postcss/postcss) from 8.5.12 to 8.5.15.
- [Release notes](https://github.com/postcss/postcss/releases)
- [Changelog](https://github.com/postcss/postcss/blob/main/CHANGELOG.md)
- [Commits](postcss/postcss@8.5.12...8.5.15)

---
updated-dependencies:
- dependency-name: postcss
  dependency-version: 8.5.15
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

package-lock.json

@@ -357,7 +357,7 @@
     "bytes": "^3.1.2",
     "css-loader": "^7.1.2",
     "file-loader": "^6.2.0",
-    "postcss": "^8.5.12",
+    "postcss": "^8.5.15",
     "postcss-loader": "^8.2.0",
     "process": "0.11.10",
     "sass": "^1.97.3",