Add documentation for line linking in Markdown (#20169)

* Add documentation for line linking in Markdown

* Slight rewording

Co-authored-by: Ethan P <56270045+ethanpalm@users.noreply.github.com>

content/github/writing-on-github/working-with-advanced-formatting/creating-a-permanent-link-to-a-code-snippet.md

@@ -13,6 +13,8 @@ topics:
   - Pull requests
 shortTitle: Permanent links to code
 ---
+## Linking to code
+
 This type of permanent link will render as a code snippet only in the repository it originated in. In other repositories, the permalink code snippet will render as a URL.
 
 ![Code snippet rendered in a comment](/assets/images/help/repository/rendered-code-snippet.png)
@@ -34,6 +36,12 @@ This type of permanent link will render as a code snippet only in the repository
 6. Paste your permalink into a comment, and click **Comment**.
   ![Pasted permalink in a comment in the same repository](/assets/images/help/repository/code-snippet-permalink-in-comment.png)
 
+## Linking to Markdown
+
+You can link to specific lines in Markdown files by loading the Markdown file without Markdown rendering. To load a Markdown file without rendering, you can use the `?plain=1` parameter at the end of the url for the file. For example, `github.com/<organization>/<repository>/blob/<branch_name>/README.md?plain=1`.
+
+You can link to a specific line in the Markdown file the same way you can in code. Append `#L` with the line number or numbers at the end of the url. For example, `github.com/<organization>/<repository>/blob/<branch_name>/README.md?plain=1#L14` will highlight line 14 in the plain README.md file.
+
 ## Further reading
 
 - "[Creating an issue](/articles/creating-an-issue/)"