Adds mark for later buttons to work index pages.
Adds mark for later buttons to the work listing pages. Cannot tell if you have already marked a work for later. Buttons will show on: Browser, tag pages, search results, collections pages, series pages, user dashboards, user works listings, bookmarks pages (won't show on bookmarks of non-AO3 works or on series bookmarks), your history pages (won't show on the saved for later page). Combine this with the AO3 mark as read script to add Mark as Read buttons to the Saved for Later page.
