📚 Update docs for url_folders option

docs/website-templates.md

@@ -78,6 +78,10 @@ Below is a table of options for each theme bundled with MyST.
 :heading-depth: 3
 ```
 
+### Site URL Options
+
+By default, MyST URLs only contain the file name for each page; folder structure is respected in the table of contents but is not reflected in URLs. If you would like to maintain nested folder structure in the URLs, you may provide the site option `url_folders: true`. This causes each folder in your MyST directory to become a path segment. For this feature to work correctly, your chosen theme must also support `url_folders` as an option. Both `book-theme` and `article-theme` bundled with MyST support this.
+
 ### Page Options
 
 Depending on the option, these can also be controlled in the frontmatter on each page under the `site` key.