Adds an event handler that runs when a key is pressed within the input field.
A dashboard number input element receives a keyPress event when a user presses a key on
the keyboard while the cursor is inside the input element. A keyPress
event is fired for printable and non-printable characters.
Notes:
Some browsers do not issue a key press event for certain keys, such as arrow keys or the shift key.
When you retrieve the value from the target property of a KeyboardEvent,
you get the value of the target element before the key was pressed.
eventHandler(event: KeyboardEvent): void The name of the function or
the function expression to run when a key is pressed.