There should be a consolidated listing of all the discussion groups

[aiuto]

The current footer has a "Stay Connected" section that points to twiter, slack, bazel-discuss@... but it omits significant other discussion

Some are:
[email protected] - general discussion and annoucements
[email protected] - technical discussion for people contributing to bazel
[email protected] - discussion specifically about external dependencies

And there are a handful of repo specific lists for rule sets.

Prompting context:
Yesterday, someone sent an e-mail to [email protected], asking to be subscribed. That obviously doesn’t work, because it’s a Google Group. After some searching on groups.google.com, I found the URL https://groups.google.com/a/bazel.build/g/external-deps that that person could use to sign up successfully. Question: is that URL documented anywhere, so that people can sign up themselves?

[aiuto]

cc: @floriographygoth