Add example of initializing an array without literal

There was no example on how to initialize an array except for using a literal. For large arrays, initialization using a literal is not really an option.

I found the array syntax on the site, but this was the piece of information that I missed. I think it might be useful for other people as well.
Why not:

    let ys = [0i, ..500];

The initializer for `xs` could be updated too.

    let xs = [1i, 2, 3, 4, 5];

I think only the first element needs the type-hint, then the compiler can infer the rest.