Fix up the add() function to support variable-length numbers

Co-authored-by: sigonasr2 <sigonasr2@gmail.com>

src/main.c

@@ -8,6 +8,6 @@
 */
 
 int main(int argc,char**argv) {
-    
+    printf("%s",add((struct String){7,"1845920"},(struct String){4,"1829"}).str);
     return 0;
 }

src/utils.c

@@ -23,7 +23,7 @@ struct String add(struct String numb1, struct String numb2){
             }
         }
     } else {
-        for (int offset=0;offset<numb1.length;offset++) {
+        for (int offset=0;offset<numb2.length;offset++) {
             str = realloc(str,++digitCount);
             //printf("Digit count is now %d\n",digitCount);
             if (numb1.length>offset) {