chore(deps): update dependency mini-css-extract-plugin to ^0.9.0 (#1634)

Author: renovate[bot]

package.json

@@ -128,7 +128,7 @@
         "markdown-it-anchor": "^5.0.0",
         "marked": "^0.8.0",
         "merge2": "^1.2.1",
-        "mini-css-extract-plugin": "^0.8.0",
+        "mini-css-extract-plugin": "^0.9.0",
         "minimist": "^1.2.0",
         "mkdirp": "^0.5.1",
         "mockdate": "^2.0.2",