Update webpack requirement to ^4.8.2 in /js

Updates the requirements on [webpack](https://github.com/webpack/webpack) to permit the latest version.
- [Release notes](https://github.com/webpack/webpack/releases)
- [Commits](https://github.com/webpack/webpack/commits/v4.8.2)

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

js/package.json

@@ -27,7 +27,7 @@
     "karma": "^1.4.1",
     "node-sass": "^4.5.3",
     "style-loader": "^0.19.1",
-    "webpack": "^3.10.0",
+    "webpack": "^4.8.2",
     "webpack-merge": "^4.1.1"
   },
   "scripts": {