message: Add first() to Arrays
diff: -export { last, allButLast, isLast };
  +export { first, last, allButLast, isLast };
  +
  +function first<T>(array: T[] | ReadonlyArray<T>): T | undefined {
  + return array[0];
  +}
  function last<T>(array: T[] | ReadonlyArray<T>): T | undefined {
  return array[array.length - 1];
  