cloud-docs rst->md conversion

[matkuliak]

What's Inside

Significant changes.

Preview

https://crate-cloud--55.org.readthedocs.build/en/55/

Highlights

• howtos - rst->md

  • reworked index to use the grid layout, added cards
  • deleted howtos/connect-to-cluster/index.md and placed the card within it directly into index.md
  • added a reference point to tutorials/quickstart

• tutorials/edge

  • converted rst->md
  • reworked index, added the cards similar to others

• reference - rst->md

  • removed subscription-plans.md as it's superseded by services

• tutorials/deploy/croud.md - rst->md

  • added a card to cannonical croud docs to make them more prominent

Checklist

• [x] Link to issue this PR refers to (if applicable): https://github.com/crate/tech-writing/issues/402
• [x] CLA is signed

[matkuliak]

Went through all the changes pretty rigorously multiple times, but it's a big change so would appreciate a review from anyone interested. Thank you in advance.

The main concern is broken links/references, although checks should catch those. Technically everything should work, quite sure of that.

[matkuliak]

Hi @amotl. Do you still need couple more days to look this over, or are you happy with it? I've got some feature docs in-progress and would like to merge this first and do them in Markdown already. Not to rush you, of course. Thanks!

[amotl]

Hi Matej. I can't find the cycles, unfortunately. I think it will be good to go, please go ahead. Thanks again!