Add info on <pre> tags to markdown reference and style guide (#35111)

Co-authored-by: Sarah Schneider <sarahs@users.noreply.github.com>

Author: ethanpalm

contributing/content-markup-reference.md

@@ -74,7 +74,7 @@ To render syntax highlighting in command line instructions, we use triple backti
 
 This syntax highlighting renders light text on a dark background, and should be reserved for command line instructions.
 
-Within the command-line syntax, use all uppercase text to indicate placeholder text or content that varies for each user, such as a user or repository name.
+Within the command-line syntax, use all uppercase text to indicate placeholder text or content that varies for each user, such as a user or repository name. By default, codeblocks will escape the content within the triple backticks. If you need to write sample code that parses the content (for example, to italicize text within `<em>` tags instead of passing the tags through literally), wrap the codeblock in `<pre>` `</pre>` tags.
 
 **Copy-able code blocks**
 

contributing/content-style-guide.md

@@ -49,6 +49,7 @@ Within code blocks:
 - Do not use markup before the command output.
 - Only use `$` before the command itself if you’re showing the command’s output in the same block.
 - If your code example includes `{` or `}` that should render, wrap that section in `{% raw %}` `{% endraw %}` to disable Liquid processing for that section.
+- If your code example includes content that should be parsed (for example, HTML tags to format text), wrap that section in `<pre>` `</pre>` tags to parse rather than escape the content in the section.
   - **Use**:
 
     ```