Community Discord/Chat landing page

[avivace]

Links to our Discord server are disseminated in a lot of places. Updating them when we revoke the invites after spam or bot waves requires effort and time to propagate the changes.

I'd like a new landing page on gbdev.io, maybe gbdev.io/chat or gbdev.io/community as the only place where we put the actual link, and then we'd link around this landing page.

Additional, in light of other recent events, this could also serve as pointer to the alternative solutions we are working on.