fix: packages/@css-blocks/website/package.json to reduce vulnerabilities (#225).

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-JS-REACTDEVUTILS-72875
- https://snyk.io/vuln/npm:extend:20180424

Author: snyk-bot

packages/@css-blocks/website/package.json

@@ -38,7 +38,7 @@
     "promise": "8.0.1",
     "raf": "3.4.0",
     "react": "^16.1.1",
-    "react-dev-utils": "^4.2.1",
+    "react-dev-utils": "^4.2.2",
     "react-dom": "^16.1.1",
     "react-ga": "^2.5.0",
     "react-router-dom": "^4.2.2",