platformModifierKey = function (mapBrowserEvent) {
  const originalEvent = mapBrowserEvent.originalEvent;
  return MAC ? originalEvent.metaKey : originalEvent.ctrlKey;
}
Return `true` if the platform-modifier-key (the meta-key on Mac,
ctrl-key otherwise) is pressed.

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