Group tags by first letter
Your task
A tag browser shows an A-to-Z index, and each letter heading displays how many tags live under it. Given a list of lowercase, non-empty tag strings (repeats allowed and counted separately), group the tags by their first letter and return a dictionary that maps each first letter (as a one-character string) to the number of tags starting with that letter. Letters with no tags must not appear in the result. For example, ["rock", "rap", "pop"] gives {"r": 2, "p": 1}.
Examples
tags_by_initial(tags: list[str]) -> dict[str,int]Example 1
Input
tags_by_initial(["rock", "rap", "pop"])Output
{"r": 2, "p": 1}