update based on PR comments

Author: emilykl

.github/pull_request_template.md

@@ -4,26 +4,27 @@ Thank you for your contribution to plotly.py!
 Please complete each section below.
 -->
 
-## Link to issue
+### Link to issue
 <!-- Link to the issue closed by this PR. If the issue doesn't exist yet, create it. -->
 
 Closes #(issue number)
 
-## Description of change
+### Description of change
 <!-- Provide a clear 1-2 sentence description of what this PR does. -->
 
-## Demo
+### Demo
 
 <!-- Include screenshots or screen recordings of this PR in action. -->
 
-## Testing strategy
+### Testing strategy
 
 <!-- Provide 1-2 sentences explaining tests added or changed by this PR. If testing changes are not needed, explain why. -->
 
-## Additional information (optional)
+### Additional information (optional)
 
 <!-- Include any additional context, background, or explanation which doesn't fit in the previous sections. -->
 
-## Guidelines
+### Guidelines
 
-- [ ] I have reviewed the [pull request guidelines](https://github.com/plotly/plotly.py/blob/main/CONTRIBUTING.md#opening-a-pull-request) and the [Code of Conduct](https://github.com/plotly/plotly.py/blob/main/CODE_OF_CONDUCT.md) and confirm that this PR follows them.
+- [ ] I have reviewed the [pull request guidelines](https://github.com/plotly/plotly.py/blob/main/CONTRIBUTING.md#opening-a-pull-request) and the [Code of Conduct](https://github.com/plotly/plotly.py/blob/main/CODE_OF_CONDUCT.md) and confirm that this PR follows them.
+- [ ] I have added an entry to the [changelog](https://github.com/plotly/plotly.py/blob/main/CHANGELOG.md) if needed (not required for documentation PRs).