Short description:
use event.altKey to check alt key pressed for support linux (and more compatibility)

Context:
I add altKeyPressed in useEffect hook to check alt key was pressed in onKeyUp handler to check alt key was pressed. because e.altKey is always false in keyup event. so I set altKeyPressed to true in onKeyDown handler and reset to false in onKeyUp handler to prevent call uninspect by other keyboard events is not alt key.

close #2