groupAnagrams = (words, map = new Map()) => {
    if (!words.length) return [];

    groupWords(words, map);    /* Time O(N * K) | Space O(N * K) */

    return [ ...map.values() ];/* Time O(N)     | Space O(N * K) */
}
Hash Map
Time O(N * K) | Space O(N * K)
https://leetcode.com/problems/group-anagrams/
@param {string[]} words
@return {string[][]}