Update Community section of Portal home page

[dcamron]

Mentioned by @jukent: our meetings & calendar sections need updating to support our new meeting structure. There are some complimentary logistics to address (meeting notes, accompanying Discourse update, etc.) that could be described here as well.

[brian-rose]

@dcamron it looks to me like this has been resolved (https://projectpythia.org/#join-us). Is more clarity still needed?

[dcamron]

Seems fine to me