Bump webpack-merge from 4.2.2 to 5.0.9 (#14424)

* Bump webpack-merge from 4.2.2 to 5.0.9

Bumps [webpack-merge](https://github.com/survivejs/webpack-merge) from 4.2.2 to 5.0.9.
- [Release notes](https://github.com/survivejs/webpack-merge/releases)
- [Changelog](https://github.com/survivejs/webpack-merge/blob/master/CHANGELOG.md)
- [Commits](https://github.com/survivejs/webpack-merge/compare/v4.2.2...v5.0.9)

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

* Fix import path

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Yamagishi Kazutoshi <ykzts@desire.sh>

package.json

@@ -166,7 +166,7 @@
     "webpack-assets-manifest": "^3.1.1",
     "webpack-bundle-analyzer": "^3.9.0",
     "webpack-cli": "^3.3.12",
-    "webpack-merge": "^4.2.1",
+    "webpack-merge": "^5.0.9",
     "wicg-inert": "^3.1.0"
   },
   "devDependencies": {