[INFRA] Maturity CS50: Add a synchronizer between GitHub discussions and the dev mailing list

[zhztheplayer]

https://community.apache.org/apache-way/apache-project-maturity-model.html

The project's traffic on the dev mailing list is low, and to follow The Apache Way, it's suggested to bring more discussions to the project's mailing list.

There is a very good reading for it - If it didn’t happen on the mailing list, it didn’t happen.

We have a number of discussions that have been happening on GitHub Discussions channel. We have synchronized them to commits@gluten.apache.org. As there are very few subscriptions of that list, we may consider synchronize them to dev@gluten.apache.org instead.

[zhztheplayer]

I'm closing this as #10896 is merged. CS50 itself is a broader topic, let's see how we can align more with it gradually.