platformModifierKeyOnly = function (mapBrowserEvent) {
  const originalEvent = mapBrowserEvent.originalEvent;
  return (
    !originalEvent.altKey &&
    (MAC ? originalEvent.metaKey : originalEvent.ctrlKey) &&
    !originalEvent.shiftKey
  );
}
Return `true` if only the platform-modifier-key (the meta-key on Mac,
ctrl-key otherwise) is pressed, `false` otherwise (e.g. when additionally
the shift-key is pressed).

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