chore(deps): update dependency optimize-css-assets-webpack-plugin to v5

Author: renovate-bot

package.json

@@ -75,7 +75,7 @@
     "markdown-loader": "3.0.0",
     "markdownlint-cli": "0.11.0",
     "mini-css-extract-plugin": "0.4.1",
-    "optimize-css-assets-webpack-plugin": "4.0.3",
+    "optimize-css-assets-webpack-plugin": "5.0.0",
     "prettier": "1.13.7",
     "prettier-package-json": "1.6.0",
     "react": "16.4.1",