Added a note for the example (#29878)

When I started learning programming for a good amount of time I couldn't understand why did we start the loop from 0 to print out values of an array, because I didn't know the "arrays are indexed from 0" rule back then. I thought this could be helpful

guide/english/c/for/index.md

@@ -42,6 +42,8 @@ int main () {
 }
 ```
 
+- It should be noted that the value of `i` is set to `0` because arrays are indexed from `0` to `size-1`, and we want to print the first value as well
+
 #### Output:
 ```shell
 > Item on index 0 is 1