Advertise the GAP slack more widely

[fingolfin]

I think the GAP slack is a very valuable resource, that should be made available to more GAP users / developers/ package authors. So:

• we could announce its existence on our mailing lists (did we do that before?)
• we could promote it on our web site

Problem is how to do it from a technical point of view: for the user, easiest would be to just offer an "invite" link (they can now be created with indefinite validity, before they expired after 30 days). However, I am concerned about spam bots using that (at least I am told other projects have that issue).

[gvol]

I didn't know GAP had a Slack workspace. How do I get an invite to it?

[hongyi-zhao]

http://gap-system.slack.com/

[fingolfin]

@gvol https://gap-system.org/slack

[fingolfin]

See also gap-system/GapWWW#272