add support for top level pages

[hariom147]

I needed to use your autopublish plugin for top level pages and therefore added them to the collection of drafts to publish respectively the collection of pages to be unpublished.

I would like to propose adding this feature to your plugin.

If for some reason I didn't think of top level pages are left out for a certain reason, I am happy to edit the code in a way that enables top level pages via an option, for example. Just let me know.

Thanks for the great plugin, it really helped me out.