chore(package): update html-webpack-plugin to version 4.2.2

Closes #17

Author: greenkeeper[bot]

package.json

@@ -16,7 +16,7 @@
     "eslint": "^5.2.0",
     "eslint-config-prettier": "^2.9.0",
     "eslint-plugin-prettier": "^2.6.2",
-    "html-webpack-plugin": "^3.2.0",
+    "html-webpack-plugin": "^4.2.2",
     "husky": "^0.14.3",
     "postcss-loader": "^2.1.6",
     "prettier": "^1.14.0",