Bump mini-css-extract-plugin from 0.4.2 to 0.4.3 in /js

Bumps [mini-css-extract-plugin](https://github.com/webpack-contrib/mini-css-extract-plugin) from 0.4.2 to 0.4.3.
- [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/v0.4.2...v0.4.3)

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

js/package.json

@@ -27,7 +27,7 @@
     "babel-preset-env": "^1.7.0",
     "css-loader": "^1.0.0",
     "karma": "^3.0.0",
-    "mini-css-extract-plugin": "^0.4.2",
+    "mini-css-extract-plugin": "^0.4.3",
     "node-sass": "^4.9.3",
     "webpack": "^4.20.2",
     "webpack-cli": "^3.1.0",