Bump postcss-mixins from 11.0.3 to 12.0.0

Bumps [postcss-mixins](https://github.com/postcss/postcss-mixins) from 11.0.3 to 12.0.0.
- [Release notes](https://github.com/postcss/postcss-mixins/releases)
- [Changelog](https://github.com/postcss/postcss-mixins/blob/main/CHANGELOG.md)
- [Commits](postcss/postcss-mixins@11.0.3...12.0.0)

---
updated-dependencies:
- dependency-name: postcss-mixins
  dependency-version: 12.0.0
  dependency-type: direct:development
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

package-lock.json

@@ -27,7 +27,7 @@
     "postcss-discard-comments": "^7.0.4",
     "postcss-each": "^1.1.0",
     "postcss-easy-import": "^4.0.0",
-    "postcss-mixins": "^11.0.3",
+    "postcss-mixins": "^12.0.0",
     "postcss-nested": "^6.2.0",
     "stylelint": "^15.10.3",
     "stylelint-config-standard": "^34.0.0",