Update usage-tips.md, note md extension for docs (#248)

docs/guides/usage-tips.md

@@ -10,7 +10,8 @@ You may also consider using the [`render_patterns` command](../reference/api.md#
 
 ## Document your patterns
 
-Patterns support defining a custom `name` in YAML, as well as rendering fully-fledged documentation in Markdown. Create a file next to the template to document it:
+Patterns support defining a custom `name` in YAML, as well as rendering fully-fledged documentation in Markdown. Create a file next to the template to document it, ensuring the filename has a `.md` extension (e.g., `call_to_action.md`):
+
 
 ```markdown
 This template can be used in different places. In streamfield block