Write a function to generate the generalized abbreviations of a word.
Note: The order of the output does not matter.
Example:
Input: "word"
Output:
["word", "1ord", "w1rd", "wo1d", "wor1", "2rd", "w2d", "wo2", "1o1d", "1or1", "w1r1", "1o2", "2r1", "3d", "w3", "4"]