Onboarding: Add acquisition question

[lmerriam]

Analytics platforms don't really tell us the whole story about how users found our service. We should consider adding a question during onboarding to learn more about this.

How did you hear about Flaredown?

• Search on google
• Friend/family told me about it
• Facebook post
• Saw it on mobile app store
• Other

[compwron]

@bklang this one could be good