[Feat] Navigation controls in the viewer page

[skoro]

The viewer currently allows to view only one item, to see another item you need to close the viewer and select the next item from the clipboard stack. It is inconvenient in order to view item by item.
That can be resolved by adding navigation icons to the viewer toolbar:

• first item
• previous item
• next item
• last item

In addition to icons, keyboard shortcuts also could be added like: Home, Left, Right, End.
Questions to be resolved:

1. The toolbar will be overfitted by icons.
2. There will be keyboard shortcuts conflict between the textarea and navigation controls.