docs(pull_request_template): make the checklist holistic

Author: bearomorphism

.github/pull_request_template.md

@@ -15,6 +15,11 @@ Please fill in the following content to let us know better about this change.
 
 - [ ] Add test cases to all the changes you introduce
 - [ ] Run `poetry all` locally to ensure this change passes linter check and tests
+- [ ] Manually test the changes:
+  - [ ] Verify the feature/bug fix works as expected in real-world scenarios
+  - [ ] Test edge cases and error conditions
+  - [ ] Ensure backward compatibility is maintained
+  - [ ] Document any manual testing steps performed
 - [ ] Update the documentation for the changes
 
 ### Documentation Changes