Outdated docs "Adding theme options"

[lumnn]

Followed "Adding theme options" tutorial on https://github.com/pagekit/docs/blob/master/tutorials/theme.md#adding-position-options

When I finished the tab "Theme" was shown, but no content inside it.

I've solved the issue by looking at theme-one code. The solution was to lower the versions of vue-loader and vue-html-loader in package.json

...
"vue-html-loader": "^1.0.0",
"vue-loader": "^8.2.0",
...