Seconds should be optional when adding a task

As the title states, a DATE field must contain the seconds attribute or else an invalid date format error is returned. A better approach would be to make seconds optional. If the date field does not contain a seconds value, it should be assumed the seconds field is 00.

cameron@Mikoshi ~> todo-cli --add-task personal "Does this even work" "Test" "2023-05-25 15:00" 0
Invalid date format.