chore: bump postcss from 8.5.15 to 8.5.18

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](postcss/postcss@8.5.15...8.5.18)

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

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

package.json

@@ -129,7 +129,7 @@
     "marked-highlight": "^2.2.4",
     "next-sitemap": "^1.9.12",
     "patch-package": "^8.0.1",
-    "postcss": "^8.5.15",
+    "postcss": "^8.5.18",
     "prettier": "^3.8.3",
     "sharp": "^0.35.0",
     "tailwindcss": "^3.4.19",

yarn.lock

@@ -7487,10 +7487,10 @@ postcss@8.4.31:
     picocolors "^1.0.0"
     source-map-js "^1.0.2"
 
-postcss@^8.4.23, postcss@^8.4.43, postcss@^8.4.47, postcss@^8.5.14, postcss@^8.5.15:
-  version "8.5.15"
-  resolved "https://registry.yarnpkg.com/postcss/-/postcss-8.5.15.tgz#d1eaf677a324e9ec02196da2d3fecf4a0b9a735c"
-  integrity sha512-FfR8sjd4em2T6fb3I2MwAJU7HWVMr9zba+enmQeeWFfCbm+UOC/0X4DS8XtpUTMwWMGbjKYP7xjfNekzyGmB3A==
+postcss@^8.4.23, postcss@^8.4.43, postcss@^8.4.47, postcss@^8.5.14, postcss@^8.5.18:
+  version "8.5.18"
+  resolved "https://registry.yarnpkg.com/postcss/-/postcss-8.5.18.tgz#8717e5a33a3b15fe8a538d2431a1e1bbbfb07614"
+  integrity sha512-xdB1oSLHbz1vRWgCDalrCqEFTWzFlhqFC5tIHLMOSUIjhm3XXQ1qrFy8S/ESr1JYRRXqM3c1QFiMZUJdUTqyMQ==
   dependencies:
     nanoid "^3.3.12"
     picocolors "^1.1.1"