Merge branch 'docs-20200123-highlighting' into 'master'

Specify syntax highlighting for shell output

See merge request gitlab-org/gitlab!23623

doc/development/documentation/styleguide.md

@@ -795,7 +795,8 @@ nicely on different mobile devices.
 - To display raw Markdown instead of rendered Markdown, you can use triple backticks
   with `md`, like the `Markdown code` example above, unless you want to include triple
   backticks in the code block as well. In that case, use triple tildes (`~~~`) instead.
-- [Syntax highlighting for code blocks](https://github.com/rouge-ruby/rouge/wiki/List-of-supported-languages-and-lexers) is available for many languages.
+- [Syntax highlighting for code blocks](https://github.com/rouge-ruby/rouge/wiki/List-of-supported-languages-and-lexers)
+  is available for many languages. Use `shell` instead of `bash` or `sh` for shell output.
 - For a complete reference on code blocks, check the [Kramdown guide](https://about.gitlab.com/handbook/product/technical-writing/markdown-guide/#code-blocks).
 
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