Ability to include custom pages in sitemap

[wanze]

Problem/Motivation SeoPro currently includes pages, entries and terms in the sitemap. This does not include routes directly rendering a template.

Proposed solution Throw an event in Sitemap::pages() allowing modules to alter pages rendered in the sitemap. This event could be used to add, modify or remove pages.

I will submit a pull request if you think the proposed solution makes sense. :)