Returns an association mapping each character to its count.
CharacterCounts["string"]
CharacterCounts["string", n]
CharacterCounts[{"string1", "string2", …}, …]
CharacterCounts["banana"]
→ <|a -> 3, n -> 2, b -> 1|>CharacterCounts["ababcab", 2]
→ <|ab -> 3, ba -> 1, bc -> 1, ca -> 1|>CharacterCounts[{"hello", "world"}]
→ {<|l -> 2, o -> 1, e -> 1, h -> 1|>, <|d -> 1, l -> 1, r -> 1, o -> 1, w -> 1|>}