Create a means of joining Slack without publicly publishing email addresses.

Creating an issue from the comment referenced below:

_Can we please get an alternative means of joining the Slack without having to publicly publish our email addresses. If this wasn't a big deal then the people in charge of it should be providing their own email addresses on here publicly so that people can email them. If that isn't desirable then it proves my point. Pretty much all other major platform communities have a way to leverage a sign up tool to submit their email address that doesn't post it publicly._

_Originally posted by @timnolte in https://github.com/devcontainers/community/discussions/3#discussioncomment-8232699_