Add link to elm community resources

[tillydray]

I'd prefer the text to only point people to the elm community page in general, and not specifically mention the mailing list. However, I decided not to delete reference to the mailing page because simply adding a reference to the elm community page seems more likely to get accepted and merged.

[ebenpack]

Yeah, seems like a nice addition.

Edit: Whoops, I closed instead of merging. Reopening and merging now.