Merge remote-tracking branch 'fosskers/colin/contributing-tweak'

CONTRIBUTING.md

@@ -7,7 +7,7 @@ Before sending patches, you are recommended to run `flake8` and `isort`.
 You can add a git hook to do this by installing `python-pre-commit` and running
 `pre-commit install`.
 
-[1] https://lists.archlinux.org/listinfo/aur-dev
+[1]: https://lists.archlinux.org/listinfo/aur-dev
 
 ### Coding Guidelines