chore(deps): bump unique-slug from 2.0.2 to 4.0.0 (#944)

Bumps [unique-slug](https://github.com/npm/unique-slug) from 2.0.2 to 4.0.0.
- [Release notes](https://github.com/npm/unique-slug/releases)
- [Changelog](https://github.com/npm/unique-slug/blob/main/CHANGELOG.md)
- [Commits](npm/unique-slug@v2.0.2...v4.0.0)

---
updated-dependencies:
- dependency-name: unique-slug
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

packages/processor/package.json

@@ -30,7 +30,7 @@
     "postcss-url": "^10.0.0",
     "postcss-value-parser": "^4.0.0",
     "resolve-from": "^5.0.0",
-    "unique-slug": "^2.0.0"
+    "unique-slug": "^4.0.0"
   },
   "peerDependencies": {
     "postcss": "^8.0.0"