chore(package): update html-webpack-plugin to version 4.2.0

Closes #43

Author: greenkeeper[bot]

package.json

@@ -125,7 +125,7 @@
     "friendly-errors-webpack-plugin": "^1.7.0",
     "fs-extra": "^8.1.0",
     "glob": "^7.1.6",
-    "html-webpack-plugin": "^3.2.0",
+    "html-webpack-plugin": "^4.2.0",
     "http-proxy-middleware": "^0.20.0",
     "hygen": "^5.0.3",
     "jest": "^24.8.0",