Added documentation to hash256.rs

hw7/task1/src/hash256.rs

 use hasher_sha256::{Hasher, HashResult};
 use hasher_sha256::Sha256;
 
-
+/// Dieser Datentyp beschreibt die Lösung des Hashverfahrens.
 pub struct Solution {
     pub number: usize,
     pub hash: String,
 }
 
+/// `verify_product` dient der Verifikation eines gefundenen Hashes.
 pub fn verify_product(base: usize, number: usize, difficulty: &String) -> Option<Solution> {
     let sol = base * number;
     let input = sol.to_string();