Re-add "Page" for all urls (also for non http(s) ones)

[Sav22999]

For non http/s urls there is no page option anymore, why? It is possible someone to want to add notes perhaps to different pages of the same addon at moz-extension://... Without the page option he won't be able to do it. I understand it is a rare case (me, I don't think I will use it) but since the functionality is already implemented and exists, why to hide it

Related to #46