chore(package): update html-webpack-plugin to version 4.0.4

Closes #13

Author: greenkeeper[bot]

package.json

@@ -30,7 +30,7 @@
     "css-loader": "^2.0.0",
     "file-loader": "^3.0.0",
     "html-webpack-inline-source-plugin": "0.0.10",
-    "html-webpack-plugin": "^3.2.0",
+    "html-webpack-plugin": "^4.0.4",
     "standard": "^12.0.1",
     "style-loader": "^0.23.0",
     "url-loader": "^1.1.1",