Allow Enter/Esc to close modals on devices with a keyboard

### Summary
When using a device with a keyboard, when pressing Enter on modals with only one input should be equivalent to clicking/tapping "OK", and pressing Esc should be equivalent to the "Cancel" button.

### Motivation

When entering data on modals, one pushes the Tab key to go to the next item, which in many cases is either the next input (think "Change Passphrase"), but quite often only the "OK" button (think "Unlock Vault").

I'd like to propose a feature where on the modals with only one input the Enter key would trigger the OK button; as opposed to the current behaviour where Enter is essentially just doing the same thing as Tab.

Also, "Esc" could trigger the "Cancel" button on pretty much every modal.

### Additional Context

This would further improve on the UX after the fix for #291.