Enable keyboard shortcuts in the BE

[tsmyre]

When I work in the Manifold BE, I find I often want to use a keyboard shortcut (like Cmd + S to save) instead of scrolling, mousing, and clicking. Beyond saving, I imagine shortcuts could also be used for navigation, to quickly move between sidebar menus or to perhaps navigate to a specific target (Cmd + D or some such to go to the Dashboard) or to motivate a specific action (Cmd + N to create a new project).