docs(contributing): do not request modifications to changelog

Author: woile

docs/contributing.md

@@ -15,7 +15,9 @@ If you're a first-time contributor, you can check the issues with [good first is
 5. Check out a new branch and add your modification.
 6. Add test cases for all your changes.
    (We use [CodeCov](https://codecov.io/) to ensure our test coverage does not drop.)
-7. Use [commitizen](https://github.com/commitizen-tools/commitizen) to do git commit.
+7. Use [commitizen](https://github.com/commitizen-tools/commitizen) to do git commit. We follow [conventional commmits][conventional-commmits]
 8. Run `./scripts/format` and `./scripts/test` to ensure you follow the coding style and the tests pass.
-9. Update `README.md` and `CHANGELOG.md` for your changes.
+9. Update `README.md`. Do **not** update the `CHANGELOG.md`, it will be automatically created after merging to `master`.
 10. Send a [pull request](https://github.com/commitizen-tools/commitizen/pulls) 🙏
+
+[conventional-commmits]: https://www.conventionalcommits.org/