Fix docs directory structure to reflect diátaxis

[davidekete]

Description

Checklist

• Runs make check successfully.
• Retains code coverage (make check-coverage).
• New/changed keys in YAML format are documented.
• (Optional) Adds example YAML for new feature.
• (Optional) Closes an open bug in Launchpad.

[rkratky]

@davidekete, thanks for submitting this! To fix the spellcheck and one cross-doc link, I submitted a PR against your branch: davidekete#3

[davidekete]

@davidekete, thanks for submitting this! To fix the spellcheck and one cross-doc link, I submitted a PR against your branch: davidekete#3

Thank you. I just merged the PR.

[rkratky]

Two notes:

• @davidekete, as discussed on Matrix, could you please rename the main/landing files in the individual categories to index.md? This naming convention is used in all other Ubuntu docs published on RTD, so it'd be good to keep it consistent. Also, it'd avoid the duplication that results from Sphinx building the landing page in two places when the index file is absent.
• @slyon, while this change in directory structure is certainly an improvement for the repo, it'll mean some existing URLs would no longer work. Therefore, we need redirects. My question is: do you think it would be enough to add redirects for the main categories only (i.e. explanation, howto, ...), or do we need redirects for all existing pages?

[slyon]

• do we need redirects for all existing pages?

I think the most important one would be the netplan-yaml reference. Maybe that in combination with the main categories. And also making sure that our website still points to the correct reference, e.g.: https://netplan.io/reference

[davidekete]

Two notes:

• @davidekete, as discussed on Matrix, could you please rename the main/landing files in the individual categories to index.md? This naming convention is used in all other Ubuntu docs published on RTD, so it'd be good to keep it consistent. Also, it'd avoid the duplication that results from Sphinx building the landing page in two places when the index file is absent.
• @slyon, while this change in directory structure is certainly an improvement for the repo, it'll mean some existing URLs would no longer work. Therefore, we need redirects. My question is: do you think it would be enough to add redirects for the main categories only (i.e. explanation, howto, ...), or do we need redirects for all existing pages?

@rkratky, I have renamed them as index.md and updated the references to match the names.