Home & Features: Add canonical feature page for "CrateDB Cloud". Update layout of entry point page.

[amotl]

About

A few improvements to Home (exists) & Features (new) pages.

• Emphasizing features of CrateDB Cloud cratedb-guide#137

Preview

• https://crate-cloud--88.org.readthedocs.build/en/88/
• https://crate-cloud--88.org.readthedocs.build/en/88/feature/

Why?

• Improve user guidance on the documentation of the Cloud product.
• People say the Database Features page may have too much gravity.
• Just a little spike to gather feedback. Use it as-is, or as a source of inspiration to build upon.

What's Inside

• Features: Add canonical feature page for "CrateDB Cloud".
  It is a compressed variant of https://cratedb.com/product/cloud.
• Features: Refactor "Learn" rubric from "Home".
• Home: Update layout of entry point page.

/cc @surister, @kneth, @ckurze, @geragray

[proddata]

I am still unclear about the purpose of the “All Features” pages. They appear to add unnecessary complexity with limited benefits, potentially creating a hurdle in the user experience.

Additionally, this specific patch seems to include outdated screenshots, which might have been taken from other parts of the documentation that also require updating.

[widmogrod]

I read through the changes. Grammatically and visually, they look good.

Refreshed CrateDB Cloud page looks nicer. Indeed, a newer screenshot could be used. But as I understand it, this is not a new asset, so maybe in a separate PR, we could refresh/modernize all images.

As for the All features page, what I found confusing is the duplication of sub-sections:

Is there a way to change it, and have all features more like a landing page that just list them? or maybe it would make more sense to merge All Features with CrateDB Cloud page (I think I like the last option)? @proddata any oppionon about it?