Use reference to coc link in CODE_OF_CONDUCT.md
# Code of Conduct
-Everyone interacting in the Cookiecutter project's codebases, issue trackers, chat
-rooms, and mailing lists is expected to follow the [PyPA Code of Conduct](https://www.pypa.io/en/latest/code-of-conduct/).
+Everyone interacting in the Cookiecutter project's codebases, issue trackers,
+chat rooms, and mailing lists is expected to follow the
+[PyPA Code of Conduct][coc].
+
+[coc]: https://www.pypa.io/en/latest/code-of-conduct/
