Use arrow keys to navigate up and down when overflow-y is scrollable

[ivanakruljac]

So, the _onKeyPressed function selects the next element, but if there is overflow-y scroll applied to the ul list,
it doesn't move the position with keycode = 38 and keycode = 40. User needs to use mouse to acually scroll thru list.

This is something that would be very nice to have :)

Many thanks!

Ivana