[A11y] Use aria-current="page" for the page menu in create-svelte template

[Tal500]

Describe the problem

It is better to use aria-current on the main page menu for accessibility, to specify what page is the current one (and the one that is the current, should be with aria-current="page").

A good side effect is that we can use the aria-current="page" as a CSS selector to style the currently active page item.

Describe the proposed solution

Use aria-current.

In Sapper demo, everything I have just said is implemented in the old Nav component, but why not in SvelteKit demos?

Alternatives considered

Not doing this :-(

Importance

nice to have

Additional Information

No response