fix: examples/brunch/package.json to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-JS-ELLIPTIC-8172694
- https://snyk.io/vuln/SNYK-JS-COOKIE-8163060

examples/brunch/package.json

@@ -15,7 +15,7 @@
     "auto-reload-brunch": "^2",
     "babel-brunch": "~6.0",
     "babel-preset-latest": "^6",
-    "brunch": "^2",
+    "brunch": "^4.0.0",
     "clean-css-brunch": "^2",
     "uglify-js-brunch": "^2"
   }