Keyboard shortcuts in the main user story map view

This is more for the power users out there... We already have keyboard shortcuts implemented in the story details modal, but it's difficult to quickly populate a brand new (empty) map using the keyboard only. I think the main thing is making it easy to see currently focussed elements and move this around with the keyboard arrows. Would be nice to add shortcuts for creating new cards, editing their titles, moving between releases, etc, too!