Add clarifications about relative links

doc/development/documentation/styleguide/index.md

@@ -998,8 +998,10 @@ To link to internal documentation:
 - Do not use absolute URLs or URLs from `docs.gitlab.com`.
 - Use `../` to navigate to higher-level directories.
 - Don't prepend `./` to links to files or directories. 
+If you need to link to a file in the same directory or in one of the sub-directories use `path/to/file.md` syntax without any prefixes.
 - Don't link relative to root. For example, `/ee/user/gitlab_com/index.md`.
 
+
   Don't:
 
   - `https://docs.gitlab.com/ee/administration/geo/replication/troubleshooting.html`
@@ -1022,6 +1024,7 @@ To link to internal documentation:
   - `../../merge_requests/index.md`
   - `../../issues/tags.md`
   - `../../issues/tags.md#stages`
+  - `issues/tags.md`
 
 NOTE:
 Using the Markdown extension is necessary for the [`/help`](../index.md#gitlab-help)