Bump webpack-cli from 3.3.4 to 3.3.6 in /app (#170)

Bumps [webpack-cli](https://github.com/webpack/webpack-cli) from 3.3.4 to 3.3.6.
- [Release notes](https://github.com/webpack/webpack-cli/releases)
- [Changelog](https://github.com/webpack/webpack-cli/blob/v3.3.6/CHANGELOG.md)
- [Commits](https://github.com/webpack/webpack-cli/compare/v3.3.4...v3.3.6)

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

app/package.json

@@ -78,7 +78,7 @@
     "typescript": "^3.2.2",
     "webpack": "^4.28.2",
     "webpack-bundle-analyzer": "^3.0.3",
-    "webpack-cli": "^3.1.2",
+    "webpack-cli": "^3.3.6",
     "webpack-dev-server": "^3.1.14"
   },
   "peerDependencies": {