To simulate keydown on document with Jest, we create a new KeyboardEvent instance.
For instance, we write
const event = new KeyboardEvent("keydown", { keyCode: 37 });
document.dispatchEvent(event);
to create a new KeyboardEvent instance with the 'keydown' event.
And we set the event object to { keyCode: 37 }.
Then we call document.dispatchEvent with the event object to dispatch the keydown event with key code 37.
