simple_get() ->
key,base_key
Read a keyboard event and return a simplified key description
Wraps get() to return either a single character for printable
keys or a shortcut string like "CTRL+c" for modified keys.
Ignores key release events.
The optional second return value base_key is the US QWERTY
equivalent of the physical key, derived from the KKBP base
field. It is non-nil only when it differs from the primary key
(i.e. when a non-Latin keyboard layout is active). Callers that
need layout-independent command dispatch (e.g. editor normal
mode) can use base_key instead of key.