341. Merge Strings Alternately

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.

Example:
Input: word1 = "abc", word2 = "pqr"
Output: "apbqcr"

Example 2:
Input: word1 = "ab", word2 = "pqrs"
Output: "apbqrs"

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