closes https://gitlab.com/minds/ux/issues/2 closes #2112 closes #2313

Testing

• logged out, go to the homepage. There's a 50/50 chance that you will either see a mobile phone on the right, or the register form. You can change it manually by modifying the experiment key in the local storage from 'base' to 'form' and vice-versa.
• everything should look like in Michael's designs, for mobile, tablets and desktop.

If you're on the homepage version with the mobile phone:

• "Join Minds Now" buttons should redirect to /onboarding where you'll only see the registration form.
• Registering should go to the next step for onboarding
• Skipping this should redirect you to homepage

If you're on the homepage version with the register form:

• Registering should redirect to the first step of the onboarding
• Skipping it should redirect to newsfeed

Testing the onboarding steps TBD

depends on engine!395