Bump webpack-merge from 5.3.0 to 5.4.0

Bumps [webpack-merge](https://github.com/survivejs/webpack-merge) from 5.3.0 to 5.4.0.
- [Release notes](https://github.com/survivejs/webpack-merge/releases)
- [Changelog](https://github.com/survivejs/webpack-merge/blob/develop/CHANGELOG.md)
- [Commits](https://github.com/survivejs/webpack-merge/compare/v5.3.0...v5.4.0)

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

package.json

@@ -18,7 +18,7 @@
     "sortablejs": "^1.12.0",
     "underscore": "^1.10.2",
     "vis": "^4.21.0",
-    "webpack-merge": "^5.3.0"
+    "webpack-merge": "^5.4.0"
   },
   "devDependencies": {
     "webpack-dev-server": "^3.11.0"