Bump mini-css-extract-plugin from 0.5.0 to 0.6.0 in /js

Bumps [mini-css-extract-plugin](https://github.com/webpack-contrib/mini-css-extract-plugin) from 0.5.0 to 0.6.0.
- [Release notes](https://github.com/webpack-contrib/mini-css-extract-plugin/releases)
- [Changelog](https://github.com/webpack-contrib/mini-css-extract-plugin/blob/master/CHANGELOG.md)
- [Commits](https://github.com/webpack-contrib/mini-css-extract-plugin/compare/v0.5.0...v0.6.0)

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

js/package.json

@@ -33,7 +33,7 @@
     "babel-loader": "^8.0.5",
     "css-loader": "^2.1.1",
     "karma": "^4.0.1",
-    "mini-css-extract-plugin": "^0.5.0",
+    "mini-css-extract-plugin": "^0.6.0",
     "style-loader": "^0.23.1",
     "uglifyjs-webpack-plugin": "^2.1.2",
     "url-loader": "^1.1.2",