feat: expose sites.json as a url

[michal-skraburski]

As per our discussion, this feature allows a participant of the webring to fetch the sites.json dynamically and implement their own logic. This has the following benefits:

• The file will be cached and reduces load on the webring parent.
• The file reduces the time it takes to load the next webring child by allowing to bypass the parent and redirect to the next/prev child.

Unfortunately I was not able to put the sites.json in public/ as Vite was throwing an error saying it was not permitted/unideal to include a file served under public/ due to bundling. I didn't fully understand this, and proceeded to offer you this equally good alternative instead. This method is still fully static.

[wiktoriavh]

i wonder if if makes sense to add a small snippet to copy as well, which already has the logic written on how to work with the sites json file. so all you would really have to do it copy the code.

<script>
// the logic...
</script>
<nav id="webring"> <!-- the html --> </nav>

[michal-skraburski]

I'll implement a little snippet to do that, no worries!