Bump webpack from 4.25.1 to 4.26.0 in /js

Bumps [webpack](https://github.com/webpack/webpack) from 4.25.1 to 4.26.0.
- [Release notes](https://github.com/webpack/webpack/releases)
- [Commits](https://github.com/webpack/webpack/compare/v4.25.1...v4.26.0)

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

js/package.json

@@ -30,7 +30,7 @@
     "karma": "^3.1.1",
     "mini-css-extract-plugin": "^0.4.5",
     "uglifyjs-webpack-plugin": "^2.0.1",
-    "webpack": "^4.25.1",
+    "webpack": "^4.26.0",
     "webpack-cli": "^3.1.2",
     "webpack-merge": "^4.1.4"
   },