You are given two strings word1 and word2. Merge the strings by adding letters in alternating order, starting with word1. If a string is longer than the other, append the additional letters onto the end of the merged string.
Return the merged string.
1 <= word1.length, word2.length <= 100word1 and word2 consist of lowercase English letters.word1 = "abc", word2 = "pqr""apbqcr"word1 = "ab", word2 = "pqrs""apbqrs"word1 = "abcd", word2 = "pq""apbqcd"