Add section on collapsible section that is open by default

content/get-started/writing-on-github/working-with-advanced-formatting/organizing-information-with-collapsed-sections.md

@@ -43,6 +43,25 @@ After a reader clicks {% octicon "triangle-right" aria-label="The right triangle
 
 ![Screenshot of the Markdown above on this page as rendered on {% data variables.product.prodname_dotcom %}, indicating that a collapsed section can contain headers, sentences of text, images, and code blocks.](/assets/images/help/writing/open-collapsed-section.png)
 
+## Creating a collapsible section that is open by default
+````markdown
+<details open>
+
+<summary>Tips for collapsible sections that are open by default</summary>
+
+### You can add a header
+
+You can add text within a collapsed section. 
+
+You can add an image or a code block, too.
+
+```python
+   print("Hello World")
+```
+
+</details>
+````
+
 ## Further reading
 
 * [{% data variables.product.prodname_dotcom %} Flavored Markdown Spec](https://github.github.com/gfm/)