Add communication spaces/events

[patcon]

There are some community/communication spaces that could probably have their own category on the website, so ppl can find the networks of ppl who interact regularly and are very interested in Polis. Here's a first pass, but maybe

• plurality institute discord
• plutality book discord?
• radicalxchange discord
• radicalxchange monthly calls (mailing list)
• compdem
  • discord/slack?
  • github discussions
  • github issues
• civic tech toronto
  • slack #polis
  • weekly hacknight meetings
  • github issues/kanban
  • notes
• codefornl
  • slack #polis
  • gitlab issues
• g0v slack #vtaiwan
• polis user group notes