Mention github discussions in CONTRIBUTING.md

Before this change, CONTRIBUTING.md proposed opening issues for questions, but this can be awkward. This change proposes instead to use the new (to this project) discussions section.

Author: szermatt

CONTRIBUTING.md

@@ -17,7 +17,7 @@ is to add it yourself as code or documentation contributions.
 
 ## Asking questions
 
-Open an issue in the [issue tracker][issues] with your question.
+Start a new [discussion][discussions] with your question.
 
 ## Documentation contributions
 
@@ -55,5 +55,6 @@ new feature and its possible implementations.
 
 [eldev]: https://emacs-eldev.github.io/eldev/
 [issues]: https://github.com/szermatt/emacs-bash-completion/issues
+[discussions]: https://github.com/szermatt/emacs-bash-completion/discussions
 [actions]: https://github.com/szermatt/emacs-bash-completion/actions
 [pulls]: https://github.com/szermatt/emacs-bash-completion/pulls