For loop JSX destructuring

[ivanjeremic]

I think there needs to be something like JSX destructuring and loops would look cleaner without a function.

Now:

<For each={items()}>
   {(item, index) => <div>id: {item.id} - index: {index}</div>}
</For>

After:

// parentheses
<For each={items()} (item, index)>
  <div>id: {item.id} - index: {index}</div>
</For>

// or curly brackets
<For each={items()} {item, index}>
  <div>id: {item.id} - index: {index}</div>
</For>

[lxsmnsyc]

Currently in conflict with #9

We can probably redesign this in a way that it doesn't have to follow the markup structure.

[Jacob-Lockwood]

Maybe this syntax with => would be more familiar?

<For each={items()} (item, index) =>
  <div>id: {item.id} - index: {index}</div>
</For>

It still has the feeling of closing the opener block because => is both an arrow and ends with >