Add fixed size array rendering

[LouisDISPA]

Hello, I was using fixed size array and the render method is not implemented on them.
I find it weird that it's implemented on Vec but not arrays. So I wrote a quick implementation.
Is there a reason it's not implemented ?

This allow to pass the array directly to the view method without converting it into a vec.

// before
view! { <div> {array.to_vec()} </div> }

// after
view! { <div> {array} </div> }

It's mostly a copy of the Vec implementation with minor adjustments :

• I removed the marker since it's used to insert new items on size change

pub struct VecState<T>
where
    T: Mountable,
{
    states: Vec<T>,
    // Vecs keep a placeholder because they have the potential to add additional items,
    // after their own items but before the next neighbor. It is much easier to add an
    // item before a known placeholder than to add it after the last known item, so we
    // just leave a placeholder here unlike zero-or-one iterators (Option, Result, etc.)
    marker: crate::renderer::types::Placeholder,
}

• I used the <[]>::map function most of the time.
  The only exception is for the future::join_all that takes and return an iterator.

• For the Render::rebuild method I don't know if there is a smart way of handling it. So I just wrote a naive implementation.

[LouisDISPA]

Here I removed 1 from the constant compared to the Vec implementation. I did this guessing that the placeholder was counted in. But I have no idea what the constant is for.

[gbj]

The 3 was the length of the comment node <!> :-) So this can just be 0, but it's also just an estimate/heuristic

[gbj]

Inserting the placeholder here will cause an issue, as it's not used during hydration (so children after this will hydrate incorrectly because there's an extra node

[gbj]

(See above)

[gbj]

Thanks so much! This looks great over all, I added a couple comments about the placeholders for information, but I just added a quick commit to fix it, so I don't think there's any action needed on your part.