Fix/improve documentation formatting

[majabojarska]

Description

Fixes markdown formatting/indentation issues to properly render via mkdocs:

• Enumeration. Several enumerated lists rendered improperly, as multiple "1." entries:
  
• Replace sequential enumeration (1. 2. 3. ...) with 1.-based enumeration. The renderer takes care of mapping the correct index to each list element. Generally easier to maintain.
• Improves readability by using admonitions, e.g.:
  
• Improves consistency of monospace formatting for package/image names.

Validation steps

1. Run mkdocs serve.
2. Open the live preview.
3. Inspect the rendered documents relevant to the PR's scope.

---

• read the CONTRIBUTING guidelines
• raised a GitHub issue or discussed it on the projects chat beforehand Not applicable
• added unit tests Not applicable
• added integration tests Not applicable
• updated documentation if needed
• updated CHANGELOG.md

[Orhideous]

#1659 may cause potential merge conflict.

[majabojarska]

I've refreshed the whole thing, rebased and resolved conflicts.

[kradalby]

@ohdearaugustin could you have a look?

[ohdearaugustin]

We just need to run prettier again

[ohdearaugustin]

It seems like that prettier will break most of the changes again.

[ohdearaugustin]

So I tried now several things that prettier won't destroy the indentation of the code-block in a list, but it seems like nothing works.

Even an ignore block like:

   <!-- prettier-ignore-start -->
   ```shell
   mkdir -p ./headscale/config
   cd ./headscale
  ```
   <!-- prettier-ignore-end -->

My assumption is that mkdocs and prettier use different markdown libraries with different standards for code blocks in lists. I really thinking to add those files just to the ignore list to get it fixed.

[ohdearaugustin]

Will merge when #1832 is fixed, then the docu should also be correctly deployed again.