Better integration with Redirection plugin

[patrickposner]

There is a feature called "URL Monitor" in the Redirection plugin, which automatically creates redirects on changing slugs for posts and pages.

These are stored in the DB table prefix_redirection_items - the relevant columns for us are URL and action_data.

We should have an integration to automatically include the root URLs (before the redirect happens) when running a static export to make redirecting pages on the static site way easier.