Bump mini-css-extract-plugin from 0.8.0 to 0.9.0 (#12674)

Bumps [mini-css-extract-plugin](https://github.com/webpack-contrib/mini-css-extract-plugin) from 0.8.0 to 0.9.0.
- [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/v0.8.0...v0.9.0)

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

package.json

@@ -109,7 +109,7 @@
     "lodash": "^4.17.14",
     "mark-loader": "^0.1.6",
     "marky": "^1.2.1",
-    "mini-css-extract-plugin": "^0.8.0",
+    "mini-css-extract-plugin": "^0.9.0",
     "mkdirp": "^0.5.1",
     "npmlog": "^4.1.2",
     "object-assign": "^4.1.1",