Bump webpack from 4.11.1 to 4.12.0 in /js

Bumps [webpack](https://github.com/webpack/webpack) from 4.11.1 to 4.12.0.
- [Release notes](https://github.com/webpack/webpack/releases)
- [Commits](https://github.com/webpack/webpack/compare/v4.11.1...v4.12.0)

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

js/package.json

@@ -24,7 +24,7 @@
     "css-loader": "^0.28.9",
     "mini-css-extract-plugin": "^0.4.0",
     "node-sass": "^4.5.3",
-    "webpack": "^4.11.1",
+    "webpack": "^4.12.0",
     "webpack-cli": "^2.1.4",
     "webpack-merge": "^4.1.2",
     "karma": "^2.0.2"