chore(deps-dev): bump postcss from 8.5.15 to 8.5.18 in /desktop/main (#460)

Bumps [postcss](https://github.com/postcss/postcss) from 8.5.15 to 8.5.18.
- [Release notes](https://github.com/postcss/postcss/releases)
- [Changelog](https://github.com/postcss/postcss/blob/main/CHANGELOG.md)
- [Commits](https://github.com/postcss/postcss/compare/8.5.15...8.5.18)

---
updated-dependencies:
- dependency-name: postcss
  dependency-version: 8.5.18
  dependency-type: direct:development
...

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desktop/main/package.json

@@ -32,7 +32,7 @@
     "@tailwindcss/typography": "^0.5.15",
     "@types/markdown-it": "^14.1.2",
     "autoprefixer": "^10.4.20",
-    "postcss": "^8.4.47",
+    "postcss": "^8.5.18",
     "sass-embedded": "^1.79.4",
     "tailwindcss": "^3.4.13",
     "typescript": "^5.8.3",