Sync current page in reader

[Dan Stillman]

https://forums.zotero.org/discussion/112687/android-1-0-0-51-pdf-state-is-not-synchronize-between-devices

Maybe we're not syncing these? The page position is stored in a lastPageIndex_* saved setting with the library and attachment item key (lastPageIndex_u_ZYI76ILE, lastPageIndex_g333_ZYI76ILH for a group).