build(deps): bump postcss from 8.5.8 to 8.5.12 in /playground (#2919)

Bumps [postcss](https://github.com/postcss/postcss) from 8.5.8 to 8.5.12.
- [Release notes](https://github.com/postcss/postcss/releases)
- [Changelog](https://github.com/postcss/postcss/blob/main/CHANGELOG.md)
- [Commits](postcss/postcss@8.5.8...8.5.12)

---
updated-dependencies:
- dependency-name: postcss
  dependency-version: 8.5.12
  dependency-type: indirect
...

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

Author: dependabot[bot]

playground/yarn.lock

@@ -2671,9 +2671,9 @@ possible-typed-array-names@^1.0.0:
   integrity sha512-/+5VFTchJDoVj3bhoqi6UeymcD00DAwb1nJwamzPvHEszJ4FpF6SNNbUbOS8yI56qHzdV8eK0qEfOSiodkTdxg==
 
 postcss@^8.5.6:
-  version "8.5.8"
-  resolved "https://registry.npmjs.org/postcss/-/postcss-8.5.8.tgz#6230ecc8fb02e7a0f6982e53990937857e13f399"
-  integrity sha512-OW/rX8O/jXnm82Ey1k44pObPtdblfiuWnrd8X7GJ7emImCOstunGbXUpp7HdBrFQX6rJzn3sPT397Wp5aCwCHg==
+  version "8.5.12"
+  resolved "https://registry.yarnpkg.com/postcss/-/postcss-8.5.12.tgz#cd0c0f667f7cb0521e2313234ea6e707a9ec1ddb"
+  integrity sha512-W62t/Se6rA0Az3DfCL0AqJwXuKwBeYg6nOaIgzP+xZ7N5BFCI7DYi1qs6ygUYT6rvfi6t9k65UMLJC+PHZpDAA==
   dependencies:
     nanoid "^3.3.11"
     picocolors "^1.1.1"