integrate #139 feature to #139 keyboard shortcut

[khad1r]

finalize feature from #138 & #139

final changelog

• added keyboard shortcut ctrl + arrow-up|down|left|right to navigate between node and center the node
• ctrl + arrow-up|down|left|right when no selected node, focus to last selected node
• navigate with ctrl + arrow-up|down|left|right behave differently than navigate with arrow-up|down|left|right

[khad1r]

I might need to adjust a few things first

[khad1r]

i've added slightly delay to appFocusIn function because when alt+tab fast enough the tab key is registered to when the mindmap became focused