Bump postcss-custom-properties from 12.1.11 to 13.3.10

Bumps [postcss-custom-properties](https://github.com/csstools/postcss-plugins/tree/HEAD/plugins/postcss-custom-properties) from 12.1.11 to 13.3.10.
- [Changelog](https://github.com/csstools/postcss-plugins/blob/main/plugins/postcss-custom-properties/CHANGELOG.md)
- [Commits](https://github.com/csstools/postcss-plugins/commits/HEAD/plugins/postcss-custom-properties)

---
updated-dependencies:
- dependency-name: postcss-custom-properties
  dependency-type: direct:development
  update-type: version-update:semver-major
...

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

package.json

@@ -123,7 +123,7 @@
     "postcss": "^8.4.31",
     "postcss-color-mod-function": "npm:@alexlafroscia/postcss-color-mod-function@^4.0.0",
     "postcss-custom-media": "^8.0.2",
-    "postcss-custom-properties": "^12.1.11",
+    "postcss-custom-properties": "^13.3.10",
     "postcss-easings": "^4.0.0",
     "postcss-import": "^15.0.0",
     "postcss-nesting": "^12.0.1",