Docs: add canonical turbo-stream example using ransack

[benkoshy]

Update: not ready to merge.

Why?

• To address this recurring issue: https://github.com/ddnexus/pagy/discussions/450
• To address the new way AJAX is being managed. #471

What I have not addressed / discussed:

• streaming using Post requests. This is currently covered by a blog post.

I have directly extracted from pagy-rails, which itself is an extraction from my experiments with turbo.

There are many ways you can return results: using turbo_frames or streams. I'm not sure which is the "correct" way - both can be used.