feat: add default template for merge request documentation

Author: tanhongit

.gitlab/merge_request_templates/default.md

@@ -0,0 +1,30 @@
+## Summary
+<!-- Describe why you made changes and the changes, including screenshots if necessary. What did you do with this pull request? -->
+
+## Unit Testing
+<!-- List your unit/integration tests here, or if there are no unit tests, please explain why. -->
+
+## Operation check
+<!-- URL of checklist, etc. -->
+
+> [!CAUTION]
+> ### Release Notes
+> <!-- * Information if you need to manually configure something at release time -->
+> <!-- * Commands to run after release, etc. -->
+> *
+
+> [!NOTE]
+> ### Additional Notes
+> <!-- * Reference information for reviewers (if there are any implementation concerns or points of note, please state them) -->
+> *
+
+## Checklist
+* [ ] Code follows our [Coding Standards](https://knowledge.cslant.com/doc/coding-standard-ascz0oLa69).
+* [ ] Code matches the confirmed solution in the ticket.
+* [ ] Unit/Integration tests have been added or updated.
+* [ ] Env/Config/DB changes were confirmed by @cslant/admin.
+
+## Additional Notes
+
+/assign me
+/draft