Documentation and communication updates

[Henning Schmiedehausen]

Team,

As you know, this mailing list is a bit quiet. We know that there is a sizable user community using Jdbi out there and we want to facilitate communication with the core development team. 

Most of us use Github as the development hub so it only feels natural to move discussions over there as well: https://github.com/jdbi/jdbi/discussions

There is no deprecation or any plans to stop using the mailing list; however chances are much better to get attention with questions or issues by adding them to the github discussions.

Thank you for using Jdbi!