Welcome message for new users

Hi all,

How about having a welcome message for new users? One where we can use markdown? We have about 40 developers in the process of migrating and we already have 5 custom slash commands and 3 webhooks that they can start using.
It will be nice that upon entering a team, a welcome message is displayed to that user. Message can be composed on the Team Settings or perhaps in the console.
That way start eliminating the need for sending emails right away.

Thanks