[v0.6] Queues & Caches

[imacrayon]

This PR introduces a new request queuing and caching system that will support client-side routing features similar to hx-boost and Hotwire's Turbo.

The queue will handle concurrency issues in situations where multiple requests could cause race conditions, like when a user is clicking faster than the server can respond, or multiple AJAX requests target the same element on the page.

The cache will store AJAX responses in memory and reuse the response on subsequent requests before requesting fresh data. The user will experience instant UI changes as they navigate between pages that have been cached.

I'd also like to introduce support for pre-fetching requests to make page navigation feel even faster.

~~I also rewrote Alpine AJAX using a class-based architecture, concepts are better organized now, and the code base is a few kBs smaller when compressed.~~ The project ended up growing considerably in size, so I reverted a lot of these changes.

So far I don't see any new APIs required to make this all work. My plan is that it will all just be automatically available after installing Alpine AJAX.

Fixes #40