-----Description----- 
This task requires writing a Lean 4 method of which given a number n and divisor d, it counts all the number that is smaller than
n whose sum of digits is divisible by d. 
-----Input-----
The input consists of three Nat:
n: Nat
d:Nat where d > 0

-----Output-----
The output is an Natural number:
Ensure this match the count that satisfy the property.

