The statement is not completely exact, because it is valid to have
both 0 non-mutable references and 1 mutable reference. Instead, use
the same wording as in mutability.md.

rust-example-rendered should be a class, not an id.

fixes rust-lang#26013

Hi

I added a little section in the for loops about the `enumerate()` function.
I think it's useful for beginners to know this function and how you can use it. 

I used the title loopcounter, but it's probably not the best word to describe it. So let me know if there is a better word :)

fixed build fail on aarch64-android
by support aarch64-android raw type definitions

The statement is not completely exact, because it is valid to have
both 0 non-mutable references and 1 mutable reference. Instead, use
the same wording as in mutability.md.

rust-example-rendered should be a class, not an id.

fixes rust-lang#26013