chore(deps): update dependency cssnano to v5

Author: renovate-bot

package.json

@@ -46,7 +46,7 @@
     "@types/jest": "24.0.12",
     "@types/puppeteer": "2.0.0",
     "@types/cssnano": "^4.0.0",
-    "cssnano": "^4.1.10",
+    "cssnano": "5.0.8",
     "autoprefixer": "^9.5.1",
     "babel-core": "7.0.0-bridge.0",
     "babel-jest": "24.7.1",