enter abstract method
Enters full-screen mode (alternate screen + raw input).
With mouseWheel, also asks the terminal to report the mouse wheel, which
the KeyDecoder turns into KeyType.wheelUp/KeyType.wheelDown. It is
opt-in because while it is on most terminals stop selecting text on a
plain drag and pasting on a middle-click (with Shift held — Option/Fn on
macOS — both still work).
Implementation
void enter({bool mouseWheel = false});