Added `-a` option which can be supplied with an article id that wallr
will open directly.
Article ids can take the absolute form of e.g. `-a 1048` opening article
with id 1048.
They can also take the relative form of e.g. `-a +2` which will open the
third-to-last entry in wallabag, i.e. count backwards from newest.
That means you can use `-a +0` for example to always directly open the
newest entry.
Renamed general reader script to `wallr`, indicating wallabag as the
underlying reader input.
Fixed listing of unread articles which showed read articles before.
Added shortcuts to sxhkd's academia mode:
the existing `r` invokes wallr with unread article display;
newly added `shift+r` invokes wallr with all articles displayed.