Write a function that turns a comma-delimited list into an array of strings.
to_array("watermelon, raspberry, orange")
➞ ["watermelon", "raspberry", "orange"]
to_array("x1, x2, x3, x4, x5")
➞ ["x1", "x2", "x3", "x4", "x5"]
to_array("a, b, c, d")
➞ ["a", "b", "c", "d"]
to_array("")
➞ []
Return an empty list for an empty string.