Preprints / Repository should be able to add custom pages

[alainna]

Is your feature request related to a problem? Please describe. As a preprints moderator / administrator, I would like to add static pages to my Janeway preprints server in addition to the base "About" page.

Describe the solution you'd like Preprint servers can also benefit from CMS's custom pages features / should be ported to repository wizard.