add a discussion tab to this repo please

[RiedleroD]

I'd like to discuss a new idea I had which doesn't work as an issue

[mmitch]

I did not even know that GitHub had a discussion tab… But we do already have a mailing list for gbsplay related things. On the other hand the mailing list is rather dead – for the last two years, the only messages were GitHub notifications (issues, commits etc.) gated to the mailing list. So I don't think we'll fracture any ongoing discussions by adding the GitHub discussions ;-)

• I've activated the Discussions tab.
• We can now discuss if we should close the mailing list and only use GitHub discussions instead (but: decentralized self-hosting vs. centralized BigEvilCorp)
• note-to-self: add Discussion notifications to the mailing list gateway

(on a personal note: for me gbsplay currently has a very low priority so I won't be quick to reply, which applies to both GitHub and the mailing list)