Add a shortcut for jumping to the next category with unread entries

[parnic]

Is your feature request related to a problem? Please describe. It would be nice if I was able to jump to the next unread category with Shift+J so that I can read through everything using only the keyboard when viewing entries outside of "All" mode. (Feedly supports this.)

Describe the solution you'd like When I am viewing a category and press Shift+J, the next category with unread entries is selected and shown. If there are no remaining unread entries, nothing happens.

If I am viewing a specific feed, the next feed with unread entries should be selected instead of the next category.

Describe alternatives you've considered Clicking with the mouse.

Additional context This mirrors a Feedly feature. Shift+K should probably do the same thing, but for the previous category.

[doowruc]

Additionally, it would be good if:

J jumps to next unread in the next feed when on last article in a feed

Mark all as read also jumps to next feed with unread