Create a function which takes in a word and spells it out, by consecutively adding letters until the full word is completed.
spelling("bee") ➞ ["b", "be", "bee"]
spelling("happy") ➞ ["h", "ha", "hap", "happ", "happy"]
spelling("eagerly") ➞ ["e", "ea", "eag", "eage", "eager", "eagerl", "eagerly"]N/A