Accessibility: Add focus option for link prefetching

[Jussi-Mannisto]

Hi,

Thanks for the great feature!

There's currently no 'focus' strategy for link prefetching, which would be a useful option for keyboard navigation.

I've created a custom component that handles this programmatically, but I'd prefer to use Inertia's link directly.

BR,
Jussi

[ncphillips]

@Jussi-Mannisto what does your component look like?