shiftKeyOnly = function (mapBrowserEvent) {
  const originalEvent = mapBrowserEvent.originalEvent;
  return (
    !originalEvent.altKey &&
    !(originalEvent.metaKey || originalEvent.ctrlKey) &&
    originalEvent.shiftKey
  );
}
Return `true` if only the shift-key is pressed, `false` otherwise (e.g. when
additionally the alt-key is pressed).

@param {import("../MapBrowserEvent.js").default} mapBrowserEvent Map browser event.
@return {boolean} True if only the shift key is pressed.
@api