Improve HackerAPI onboarding experience

[pierreTklein]

We should create a better onboarding experience than what is currently documented in https://github.com/hackmcgill/docs/blob/master/db/dev-settings.md

Imagine if we had npm run first-time-setup or something, and it did the following via CLI:

1. Guides you through setup of .env file
2. Runs npm run seed
3. Asks for the email + password for the first admin account, and then creates the account