Allow 'f'+'F' binding while in 'v' (visual) to enter selection mode

[DavidLGoldberg]

It'd be nice to allow the hotkeys to continue and pick up on the selection modes. (command palette works fine so it's just a binding precedence issue)

the 'f' key should also work to continue selection. Once the keybindings are worked out, 'f' should work IF #45 is already built.