Given a list of integers, determine whether the sum of its elements is even or odd.
The return value should be a string ("odd" or "even").
If the input list is empty, consider it as a list with a zero ([0]).
even_or_odd([0]) ➞ "even"
even_or_odd([1]) ➞ "odd"
even_or_odd([]) ➞ "even"
even_or_odd([0, 1, 5]) ➞ "even"
N/A