Arrow keys and 'Enter' support for q-list

[jitendra1607]

Suppose i have 100 items in qlist, I want to autofocus 1st element and then arrow up/down key navigation. After focussing desired item pressing 'enter' should work too. During the down navigation if an item is not in visible range then the list should scroll down a little bit before focussing next item. This is generic behaviour and should exist in q-list by default.