chore(deps): bump postcss from 8.4.23 to 8.4.31 in /example (#211)

Bumps [postcss](https://github.com/postcss/postcss) from 8.4.23 to 8.4.31.
- [Release notes](https://github.com/postcss/postcss/releases)
- [Changelog](https://github.com/postcss/postcss/blob/main/CHANGELOG.md)
- [Commits](postcss/postcss@8.4.23...8.4.31)

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

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Author: dependabot[bot]

example/yarn.lock

@@ -7142,9 +7142,9 @@ postcss-value-parser@^4.1.0, postcss-value-parser@^4.2.0:
   integrity sha512-1NNCs6uurfkVbeXG4S8JFT9t19m45ICnif8zWLd5oPSZ50QnwMfK+H3jv408d4jw/7Bttv5axS5IiHoLaVNHeQ==
 
 postcss@^8.3.5, postcss@^8.4.21:
-  version "8.4.23"
-  resolved "https://registry.yarnpkg.com/postcss/-/postcss-8.4.23.tgz#df0aee9ac7c5e53e1075c24a3613496f9e6552ab"
-  integrity sha512-bQ3qMcpF6A/YjR55xtoTr0jGOlnPOKAIMdOWiv0EIT6HVPEaJiJB4NLljSbiHoC2RX7DN5Uvjtpbg1NPdwv1oA==
+  version "8.4.31"
+  resolved "https://registry.yarnpkg.com/postcss/-/postcss-8.4.31.tgz#92b451050a9f914da6755af352bdc0192508656d"
+  integrity sha512-PS08Iboia9mts/2ygV3eLpY5ghnUcfLV/EXTOW1E2qYxJKGGBUtNjN76FYHnMs36RmARn41bC0AZmn+rR0OVpQ==
   dependencies:
     nanoid "^3.3.6"
     picocolors "^1.0.0"