Review and improve SDC documentation

I tagging this to maybe get a novice contributor to go through the documentation on the contribution day at Drupalcon. Lille

I am working on this issue at DrupalCon Lille today.

Now that this documentation is more extensive, should this issue be broken up into multiple child issues? We probably don't need a child issue for every page, but perhaps at least the first 4 should have their own issues. (About Single Directory Components, Quickstart, Creating a single-directory component, Using your new single-directory component).

For reference there is already an issue for some of this, see related.

I'm at DrupalCon ATL revising the Quickstart → page as part of mentored mentorship (with @kwiseman and @igorgoncalves).

working with @bember and @kwiseman at #Atlanta2025

It would be helpful to list the pages that are being worked on in the issue summary or in a comment as you are working on them so we can track what pages have been worked on.

I am working on Quickstart page during DrupalCon Atlanta 2025 with KWiseman.