Representations of pressable keys that aren't text.
These are stored in the Unicode PUA (Private Use Area) code points.
NULL
CANCEL
HELP
BACKSPACE
TAB
CLEAR
RETURN_KEY
ENTER
SHIFT
LEFT_SHIFT
CONTROL
LEFT_CONTROL
ALT
LEFT_ALT
PAUSE
ESCAPE
SPACE
PAGE_UP
PAGE_DOWN
END
HOME
LEFT
ARROW_LEFT
UP
ARROW_UP
RIGHT
ARROW_RIGHT
DOWN
ARROW_DOWN
INSERT
DELETE
SEMICOLON
EQUALS
NUMPAD0
NUMPAD1
NUMPAD2
NUMPAD3
NUMPAD4
NUMPAD5
NUMPAD6
NUMPAD7
NUMPAD8
NUMPAD9
MULTIPLY
ADD
SEPARATOR
SUBTRACT
DECIMAL
DIVIDE
F1
F2
F3
F4
F5
F6
F7
F8
F9
F10
F11
F12
META
COMMAND
ZENKAKU_HANKAKU
encode( $keys) : array
Encode input of `sendKeys()`.