Bump webpack-cli from 3.3.12 to 4.0.0

Bumps [webpack-cli](https://github.com/webpack/webpack-cli) from 3.3.12 to 4.0.0.
- [Release notes](https://github.com/webpack/webpack-cli/releases)
- [Changelog](https://github.com/webpack/webpack-cli/blob/master/CHANGELOG.md)
- [Commits](https://github.com/webpack/webpack-cli/compare/v3.3.12...webpack-cli@4.0.0)

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

Author: dependabot[bot]

package.json

@@ -107,7 +107,7 @@
     "url-loader": "^4.1.1",
     "watchify": "^3.11.1",
     "webpack": "^4.41.2",
-    "webpack-cli": "^3.3.10",
+    "webpack-cli": "^4.0.0",
     "webpack-dev-middleware": "^3.7.2",
     "webpack-node-externals": "^1.7.2"
   },