src/vs/editor/common/config/editorOptions.ts/_multiCursorModifierFromString
function _multiCursorModifierFromString(multiCursorModifier: 'ctrlCmd' | 'alt'): 'altKey' | 'metaKey' | 'ctrlKey' {
	if (multiCursorModifier === 'ctrlCmd') {
		return (platform.isMacintosh ? 'metaKey' : 'ctrlKey');
	}
	return 'altKey';
}