Improve new member onboarding

Currently when a new member joins the slack group we send a welcome message and invite them to update their slack profile. I think it would be a better experience if we initiate a private conversation afterwards and:

• [ ] give information on who we are and what we're about
• [ ] inform them of code of conduct
• [ ] give a quick slack tutorial
• [ ] inform of them who the admins are
• [ ] show them interesting channels to join
• [ ] inform them of our community projects
• [ ] ask more info about them and what they do and use the slack api to update their profile on their behalf, after getting the user's consent to do so

I don't think it is our place to give a quick slack tutorial.