refactoring: added descriptions to a function

src/arithmeticMultiplication_Double.c

@@ -7,6 +7,6 @@ double* multiplication_double(double a, double b) {
     if (result == NULL) {
         return NULL; // Handle memory allocation failure
     }
-    *result = a * b;
+    *result = a * b; // we multiply a times b and the result gets saved in *result
     return result;
 }