docs(poppins): #15 add docs making this a Poppins project

[tiagostutz]

• Add to README the final guidelines to make this a Poppins beginner's friendly project.

I crated the issue #21 because this is part of Poppins manifesto. Could you please pin the issue and add the labels:

• first-timers-only
• good first issue

All of this is to help people that is looking for contribute to an open source project to arrive here.

Closes #15