chore: add explanation of ascii magic

cprNumber/main.cpp

@@ -10,6 +10,13 @@ int main(){
     int con = 0;
     int mult[] = {4,3,2,7,6,5,4,3,2,1};
     for (int i = 0; i< cprNum.length(); ++i){
+        // ASCII magic to convert a char of an int to its int value
+        // this will only work for values 0-9
+        // cprNum[i] holds the current character value of the integers we get from the input
+        // let's substitute in a value for cprNum[i] as an example
+        // '0' in ASCII is 48
+        // we'll use the number 3, its ASCII value is 51
+        // '3' - '0' = 51 - 48 = 3 
         con = cprNum[i] - '0';
         sum += con * mult[i];
     }