Fix `doom publish` pipeline for (docs|wiki).doomemacs.org

> [!IMPORTANT]
>
> This is a [roadmap](https://doomemacs.org/roadmap) issue and is used solely to announce and document progress (to make it easier for users to follow and maintainers to track). Please do not use it for discussion; use [our discussion board](https://doomemacs.org/discuss) instead.

The old pipeline was a juryrigged and unscalable mess (under `doom make docs:html`), so I'm generalizing it into a less specialized `doom publish` command (which will effectively be a CLI to `org-publish` plus some augmentations), which should feel familiar to static site generators and is configurable either through command line options, a `.doom` project config file, or globally from your `$DOOMDIR/{init,cli}.el`.

This roadmap issue only tracks the completion of the `doom publish` command and the configuration for `docs.doomemacs.org` and `wiki.doomemacs.org`, but not the new content destined for these two sites (those will be tracked in separate issues).

## Tasks

- [ ] Add the new `doom publish` command to Doom's CLI
- [ ] Fix the CI/CD pipeline for docs.doomemacs.org
- [ ] Fix the CI/CD pipeline for wiki.doomemacs.org