Bump webpack-merge from 4.1.4 to 4.1.5 in /js

Bumps [webpack-merge](https://github.com/survivejs/webpack-merge) from 4.1.4 to 4.1.5.
- [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/commits)

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

js/package.json

@@ -32,7 +32,7 @@
     "uglifyjs-webpack-plugin": "^2.0.1",
     "webpack": "^4.26.1",
     "webpack-cli": "^3.1.2",
-    "webpack-merge": "^4.1.4"
+    "webpack-merge": "^4.1.5"
   },
   "scripts": {
     "build": "./node_modules/webpack-cli/bin/cli.js --mode production --config webpack.prod.config.js",