Bump webpack-merge from 4.1.3 to 4.1.4 in /js

Bumps [webpack-merge](https://github.com/survivejs/webpack-merge) from 4.1.3 to 4.1.4.
- [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/v4.1.3...v4.1.4)

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

js/package.json

@@ -30,7 +30,7 @@
     "node-sass": "^4.9.2",
     "webpack": "^4.16.5",
     "webpack-cli": "^3.1.0",
-    "webpack-merge": "^4.1.3"
+    "webpack-merge": "^4.1.4"
   },
   "scripts": {
     "build": "./node_modules/webpack-cli/bin/cli.js --mode production --config webpack.prod.config.js",