Similar to the keybindings added to the info layer in PR #14188, I here propose to add the same
keybindings to the epub layer. These J/K keybindings are currently undefined in the epub
layer. These keybindings are used in the Zathura document reader, they are very
convenient and I guess they feel very natural and are preferred over d/u by most people.
Add `d` and `u` for scrolling down and up, just like the `pdf` layer.
Those are actually default `nov` keybings.
Invert `up` and `down` `nov` commands
Add keybindings in epub layer docs
Align table
