[feature] make a new account post a "first steps guide" toot
When an account got created, a user might be a bit lost, mistaking the group account with an individual account.
The account could be ordered to post a first (or receive a direct message) containing indications on how to:
- configure the group (visibility of toots => private/public, )
- how one may post in the newly created group
- recommend to toot about the newly created group