Docs: add the documentation guidelines into its own dir

CONTRIBUTING.md

@@ -512,7 +512,7 @@ request is as follows:
 1. Write [tests](https://docs.gitlab.com/ee/development/rake_tasks.html#run-tests) and code
 1. [Generate a changelog entry with `bin/changelog`][changelog]
 1. If you are writing documentation, make sure to follow the
-   [documentation styleguide][doc-styleguide]
+   [documentation guidelines][doc-guidelines]
 1. If you have multiple commits please combine them into a few logically
   organized commits by [squashing them][git-squash]
 1. Push the commit(s) to your fork
@@ -727,7 +727,7 @@ available at [http://contributor-covenant.org/version/1/1/0/](http://contributor
 [rss-source]: https://github.com/bbatsov/ruby-style-guide/blob/master/README.md#source-code-layout
 [rss-naming]: https://github.com/bbatsov/ruby-style-guide/blob/master/README.md#naming
 [changelog]: doc/development/changelog.md "Generate a changelog entry"
-[doc-styleguide]: doc/development/doc_styleguide.md "Documentation styleguide"
+[doc-guidelines]: doc/development/documentation/index.md "Documentation guidelines"
 [js-styleguide]: doc/development/fe_guide/style_guide_js.md "JavaScript styleguide"
 [scss-styleguide]: doc/development/fe_guide/style_guide_scss.md "SCSS styleguide"
 [newlines-styleguide]: doc/development/newlines_styleguide.md "Newlines styleguide"

doc/README.md

@@ -215,7 +215,7 @@ Learn how to contribute to GitLab:
 
 - [Development](development/README.md): All styleguides and explanations how to contribute.
 - [Legal](legal/README.md): Contributor license agreements.
-- [Writing documentation](development/writing_documentation.md): Contributing to GitLab Docs.
+- [Writing documentation](development/documentation/index.md): Contributing to GitLab Docs.
 
 ## GitLab subscriptions
 

doc/articles/index.md

@@ -4,7 +4,7 @@ comments: false
 
 # Technical articles list (deprecated)
 
-[Technical articles](../development/writing_documentation.md#technical-articles) are
+[Technical articles](../development/documentation/index.md#technical-articles) are
 topic-related documentation, written with an user-friendly approach and language, aiming
 to provide the community with guidance on specific processes to achieve certain objectives.
 

doc/development/README.md

@@ -88,8 +88,8 @@ description: 'Learn how to contribute to GitLab.'
 
 ## Documentation guides
 
-- [Writing documentation](writing_documentation.md)
-- [Documentation styleguide](doc_styleguide.md)
+- [Writing documentation](documentation/index.md)
+- [Documentation styleguide](documentation/styleguide.md)
 - [Markdown](../user/markdown.md)
 
 ## Internationalization (i18n) guides

doc_styleguide.md

-# Documentation styleguide
-
-Moved to [development/doc_styleguide](doc/development/doc_styleguide.md).