Bump schema-utils from 2.7.1 to 3.1.1

Bumps [schema-utils](https://github.com/webpack/schema-utils) from 2.7.1 to 3.1.1.
- [Release notes](https://github.com/webpack/schema-utils/releases)
- [Changelog](https://github.com/webpack/schema-utils/blob/master/CHANGELOG.md)
- [Commits](webpack/schema-utils@v2.7.1...v3.1.1)

---
updated-dependencies:
- dependency-name: schema-utils
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

package.json

@@ -17,7 +17,7 @@
     "imagemin": "^7.0.1",
     "loader-utils": "^2.0.0",
     "object-assign": "^4.1.1",
-    "schema-utils": "^2.7.1"
+    "schema-utils": "^3.1.1"
   },
   "optionalDependencies": {
     "imagemin-gifsicle": "^7.0.0",