chore: Expand and organize GitLab Duo MR review instructions
This is a followup to @dnsmichi's change to introduce MR Instructions for the handbook, originally added in !16632 (merged).
It's also related to gitlab-com/gl-infra/common-template-copier!536 (merged), in which we're introduce templated MR Instructions across all Infrastructure Platforms projects.
Why
One of the things that really excites me about using LLMs for documentation reviews is that they can help with things that traditional linters, spellcheckers, and prose checkers are unable to help with: style and language form.
With this in mind, I took the GitLab Brand Voice Guidelines and Writing Style guidelines and integrated it into the mr-instructions for markdown content.
I've also kept the existing rules, although I had to move them around to ensure that they're in the right sections which have been introduced.
Sidenote
Using LLMs for reviews have incredible potential, but I think we should be wary of using them for the things they're good at while avoiding them for things their bad at. Just looking at the @GitLabDuo review for this MR is a perfect example of where LLMs fail: they do a poor and inconsistent job at handling things that linters and static analysis tools excel at. In the case of this MR, @GitLabDuo is incorrectly raising errors for markdown structure and indenting that a linter can detect much more accurately.
As such, we should try to use @GitLabDuo for higher order analysis such as whether a document is well structured in its arguments and descriptions and well written, rather than linting and static analysis tasks.
Linters perform the role is linting and are much cheaper to run and more reliable. We should use them for that. LLMs can provide a great deal of value, with higher order analysis, and we should focus on using them for that.
What
Restructure the Content review section with comprehensive style guidelines organized into clear categories (Writing Style, Localization, Document Structure, etc.). Fix sequential numbering (1-45) and ensure the file follows its own guidelines by replacing Latin abbreviations with "for example" and converting passive voice to active voice throughout.